Calculation and analysis of burnup and optimum core design in accelerator driven sub-critical system

International Nuclear Information System (INIS)

Wang Yuwei; Yang Yongwei; Cui Pengfei

2011-01-01

The premise of the accelerator driven sub-critical system (ADS) in the accident is still subcritical, the biggest k eff change with burn time is less than 1.5% and the cladding material, HT9 steel, can withstand the maximum radiation damage, core fuel area is divided into fuel transmutation area and fuel multiplication area, and fuel transmutation area maintains the same fuel composition in the whole process. Through the analysis of the composition of the fuel, shape of core layout and the power distribution, etc., supposed outer and inner Pu enrichment ratio range of 1.0-1.5, then the fuel components of fuel multiplication area was adjusted. Time evolution of k eff was calculated by COUPLED2 which coupled with MCNP and ORIGEN. At the same time the power peaking factors, minoractinides transmutation rate desired to maximization and burnup were considered. A sub-critical system fitting for engineering practice was established. (authors)

Reactor noise in critical and accelerator driven sub-critical systems

International Nuclear Information System (INIS)

Degweker, S.B.; Rana, Y.S.

2007-01-01

Noise methods have long been used for reactor kinetics parameters measurement and as diagnostic tools for monitoring the health of a nuclear power plant. It is conceivable that noise techniques would find similar applications in ADS. Measurement/monitoring the degree of sub-criticality of an ADS is one such application for which noise based methods are being considered, among others such as the pulsed source method. For this reason, theoretical studies on ADS noise have appeared since the late nineties. The principal difference between critical reactor noise and ADS noise is due to the statistical properties of the source. Unlike the source due to radioactive decay present in ordinary reactors, the machine produced ADS source cannot be assumed to be a Poisson process. In addition the source is pulsed. All this requires a new theoretical approach to the subject. In a number of papers (beginning in 2000) such a theoretical approach has been developed in BARC. Over the years, our approach has received general acceptance. The paper gives a description of the subject of reactor noise and its applications in critical reactors. The theory of noise in ADS is then outlined, highlighting the differences in approach and results from that of critical reactors. (author)

Neutronic design and analysis on dual-cooled waste transmutation blanket for the fusion driven sub-critical system

International Nuclear Information System (INIS)

Zheng Shanliang; Wu Yican; Gao Chunjing; Xu Dezheng; Li Jingjing; Zhu Xiaoxiang

2004-01-01

Neutronics design and analysis of dual-cooled multi-functional waste transmutation blanket (DWTB) for the fusion driven sub-critical system (FDS) are performed to ensure the system be able to meet the requirements of fuel-sufficiency and more waste transmutation ratio with low initial loading fuel inventory, which is based on 1-D burn-up calculations with home-developed code Visual BUS and the multi-group (175 neutron groups-42 Gamma groups coupled) data library HENDL1.0/MG (Hybrid Evaluated Nuclear Data Library). (authors)

High pressure driven superconducting critical temperature tuning in Sb{sub 2}Se{sub 3} topological insulator

Energy Technology Data Exchange (ETDEWEB)

Anversa, Jonas [Departamento de Física, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS (Brazil); Escola de Engenharia Civil, Faculdade Meridional, 99070-220, Passo Fundo, RS (Brazil); Chakraborty, Sudip, E-mail: sudiphys@gmail.com [Condensed Matter Theory Group, Department of Physics and Astronomy, Box 516, Uppsala University, S-75120 Uppsala (Sweden); Piquini, Paulo [Departamento de Física, Universidade Federal de Santa Maria, 97105-900, Santa Maria, RS (Brazil); Ahuja, Rajeev [Condensed Matter Theory Group, Department of Physics and Astronomy, Box 516, Uppsala University, S-75120 Uppsala (Sweden); Applied Materials Physics, Department of Materials and Engineering, Royal Institute of Technology (KTH), S-100 44 Stockholm (Sweden)

2016-05-23

In this letter, we are reporting the change of superconducting critical temperature in Sb{sub 2}Se{sub 3} topological insulator under the influence of an external hydrostatic pressure based on first principles electronic structure calculations coupled with Migdal–Eliashberg model. Experimentally, it was shown previously that Sb{sub 2}Se{sub 3} was undergoing through a transition to a superconducting phase when subjected to a compressive pressure. Our results show that the critical temperature increases up to 6.15 K under the pressure unto 40 GPa and, subsequently, drops down until 70 GPa. Throughout this pressure range, the system is preserving the initial Pnma symmetry without any structural transformation. Our results suggest that the possible relevant mechanism behind the superconductivity in Sb{sub 2}Se{sub 3} is primarily the electron–phonon coupling.

Noise method for monitoring the sub-criticality in accelerator driven systems

International Nuclear Information System (INIS)

Rugama, Y.; Munoz-Cobo, J.L.; Valentine, T.E.; Mihalczo, J.T.; Perez, R.B.; Perez-Navarro, A.

2001-01-01

In this paper, an absolute measurements technique for the sub-criticality determination is presented. The development of ADS, requires of methods to monitor and control the sub-criticality of this kind of systems, without interfering it's normal operation mode. This method is based on the Stochastic Neutron and Photon Transport Theory developed by Munoz-Cobo et al., and which can be implemented in presently available neutron transport codes. As a by-product of the methodology a monitoring measurement technique has been developed and verified using two coupled Monte Carlo programs. The spallation collisions and the high-energy transport are simulated with LAHET. The neutrons transports with energies less than 20 MeV and the estimation of the count statistics for neutron and/or gamma ray counters in fissile systems, is simulated with MCNP-DSP. It is possible to get the kinetics parameters and the k eff value of the sub-critical system through the analysis of the counter detectors. (author)

Critical and sub-critical experiments on U-BeO lattices; Experiences critiques et sous-critiques sur reseaux U-BeO

Energy Technology Data Exchange (ETDEWEB)

Benoist, P.; Gourdon, Ch.; Martelly, J.; Sagot, M.; Wanner, G. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Deniz, V.; Joshi, B.V.; Sahai, K. [Atomic Energy Establishment Trombay (India)

1958-07-01

Sub-critical experiments have allowed us to measure the material buckling of uranium natural oxide of beryllium lattices with a grid of 15 cm, and made up of uranium bars measuring 2.60 - 2.92 - 3.56 and 4.40 cm of diameter. A critical experiment has then been conducted with hollow 1.35 per cent enriched uranium bars. A study of U-BeO 18.03 cm grid lattices is at present being conducted. (author)Fren. [French] Nous avons mesure par des experiences sous-critiques le laplacien matiere de reseaux uranium naturel-oxyde de beryllium, dont la maille carree a un pas de 15 cm, realises avec des barreaux d'uranium de diametres 2,60 - 2,92 - 3,56 - 4,40 cm. Une experience critique a ete faite ensuite avec des barres creuses d'uranium enrichi a 1,35 pour cent; l'etude des reseaux U-BeO de pas 18,03 cm est actuellement en cours. (auteur)

Critical and sub-critical experiments on U-BeO lattices; Experiences critiques et sous-critiques sur reseaux U-BeO

Energy Technology Data Exchange (ETDEWEB)

Benoist, P; Gourdon, Ch; Martelly, J; Sagot, M; Wanner, G [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires; Deniz, V; Joshi, B V; Sahai, K [Atomic Energy Establishment Trombay (India)

1958-07-01

Sub-critical experiments have allowed us to measure the material buckling of uranium natural oxide of beryllium lattices with a grid of 15 cm, and made up of uranium bars measuring 2.60 - 2.92 - 3.56 and 4.40 cm of diameter. A critical experiment has then been conducted with hollow 1.35 per cent enriched uranium bars. A study of U-BeO 18.03 cm grid lattices is at present being conducted. (author)Fren. [French] Nous avons mesure par des experiences sous-critiques le laplacien matiere de reseaux uranium naturel-oxyde de beryllium, dont la maille carree a un pas de 15 cm, realises avec des barreaux d'uranium de diametres 2,60 - 2,92 - 3,56 - 4,40 cm. Une experience critique a ete faite ensuite avec des barres creuses d'uranium enrichi a 1,35 pour cent; l'etude des reseaux U-BeO de pas 18,03 cm est actuellement en cours. (auteur)

Evaluation of Saxton critical experiments

Energy Technology Data Exchange (ETDEWEB)

Joo, Hyung Kook; Noh, Jae Man; Jung, Hyung Guk; Kim, Young Il; Kim, Young Jin [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

1998-12-31

As a part of International Criticality Safety Benchmark Evaluation Project (ICSBEP), SAXTON critical experiments were reevaluated. The effects of k{sub eff} of the uncertainties in experiment parameters, fuel rod characterization, soluble boron, critical water level, core structure, {sup 241}Am and {sup 241}Pu isotope number densities, random pitch error, duplicated experiment, axial fuel position, model simplification, etc., were evaluated and added in benchmark-model k{sub eff}. In addition to detailed model, the simplified model for Saxton critical experiments was constructed by omitting the top, middle, and bottom grids and ignoring the fuel above water. 6 refs., 1 fig., 3 tabs. (Author)

Evaluation of Saxton critical experiments

Energy Technology Data Exchange (ETDEWEB)

Joo, Hyung Kook; Noh, Jae Man; Jung, Hyung Guk; Kim, Young Il; Kim, Young Jin [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

1997-12-31

As a part of International Criticality Safety Benchmark Evaluation Project (ICSBEP), SAXTON critical experiments were reevaluated. The effects of k{sub eff} of the uncertainties in experiment parameters, fuel rod characterization, soluble boron, critical water level, core structure, {sup 241}Am and {sup 241}Pu isotope number densities, random pitch error, duplicated experiment, axial fuel position, model simplification, etc., were evaluated and added in benchmark-model k{sub eff}. In addition to detailed model, the simplified model for Saxton critical experiments was constructed by omitting the top, middle, and bottom grids and ignoring the fuel above water. 6 refs., 1 fig., 3 tabs. (Author)

Neutronics optimization of LiPb-He dual-cooled fuel breeding blanket for the fusion-driven sub-critical system

International Nuclear Information System (INIS)

Zheng Shanliang; Wu Yican

2002-01-01

The concept of the liquid Li 17 Pb 83 and Helium gas dual-cooled Fuel Breeding Blanket (FBB) for the Fusion-Driven sub-critical System (FDS) is presented and analyzed. Taking self-sustaining tritium (TBR > 1.05) and annual output of 100 kg or more fissile 239 Pu (FBR > 0.238) as objective parameters, and based on the three-dimensional Monte Carlo neutron-photon transport code MCNP/4A, a neutronics-optimized calculation of different cases was carried out and the concept is proved feasible. In addition, the total breeding ratio (Br = Tbr + Fbr) is listed corresponding to different cases

K/sub infinity/-meter concept verified via subcritical-critical TRIGA experiments

International Nuclear Information System (INIS)

Ocampo Mansilla, H.

1983-01-01

This work presents a technique for building a device to measure the k/sub infinity/ of a spent nuclear fuel assembly discharged from the core of a nuclear power plant. The device, called a k/sub infinity/-meter, consists of a cross-shaped subcritical assembly, two artificial neutron sources, and two separate neutron counting systems. The central position of the subcritical assembly is used to measure k/sub infinity/ of the spent fuel assembly. The initial subcritical assembly is calibrated to determine its k/sub eff/ and verify the assigned k/sub infinity/ of a selected fuel assembly placed in the central position. Count rates are taken with the fuel assembly of known k/sub infinity/'s placed in the central position and then repeated with a fuel assembly of unknown k/sub infinity/ placed in the central position. The count rate ratio of the unknown fuel assembly to the known fuel assembly is used to determine the k/sub infinity/ of the unknown fuel assembly. The k/sub infinity/ of the unknown fuel assembly is represented as a polynomial function of the count rate ratios. The coefficients of the polynomial equation are determined using the neutronic codes LEOPARD and EXTERMINATOR-II. The analytical approach has been validated by performing several subcritical/critical experiments, using the Penn State Breazeale TRIGA Reactor (PSBR), and comparing the experimental results with the calculations

Insulating phase in Sr{sub 2}IrO{sub 4}: An investigation using critical analysis and magnetocaloric effect

Energy Technology Data Exchange (ETDEWEB)

Bhatti, Imtiaz Noor; Pramanik, A.K., E-mail: akpramanik@mail.jnu.ac.in

2017-01-15

The nature of insulating phase in 5d based Sr{sub 2}IrO{sub 4} is quite debated as the theoretical as well as experimental investigations have put forward evidences in favor of both magnetically driven Slater-type and interaction driven Mott-type insulator. To understand this insulating behavior, we have investigated the nature of magnetic state in Sr{sub 2}IrO{sub 4} through studying critical exponents, low temperature thermal demagnetization and magnetocaloric effect. The estimated critical exponents do not exactly match with any universality class, however, the values obey the scaling behavior. The exponent values suggest that spin interaction in present material is close to mean-field model. The analysis of low temperature thermal demagnetization data, however, shows dual presence of localized- and itinerant-type of magnetic interaction. Moreover, field dependent change in magnetic entropy indicates magnetic interaction is close to mean-field type. While this material shows an insulating behavior across the magnetic transition, yet a distinct change in slope in resistivity is observed around T{sub c}. We infer that though the insulating phase in Sr{sub 2}IrO{sub 4} is more close to be Slater-type but the simultaneous presence of both Slater- and Mott-type is the likely scenario for this material. - Highlights: • Critical analysis shows Sr{sub 2}IrO{sub 4} has ferromagnetic ordering temperature T{sub c}~225 K. • Obtained critical exponents imply spin interaction is close to mean-field model. • Analysis of magneto-entropy data also supports mean-field type interaction. • However, the presence of both itinerant and localized spin interaction is evident. • Sr{sub 2}IrO{sub 4} has simultaneous presence of both Slater- and Mott-type insulating phase.

Comparison of the transient behavior of lead-based advanced critical and sub-critical reactors

International Nuclear Information System (INIS)

Wang Gang; Gu Zhixing; Wang Zhen; Jin Ming; Bai Yunqing

2014-01-01

A lead-based reactor developed by FDS Team is proposed in 2011 and designed to be 10 MW. It is a pool type reactor and the primary coolant is driven by natural circulation. The reactor has two operation modes, which are a lead-based critical fast reactor mode and a lead-based sub-critical reactor mode. The conceptual designs of the two modes are both completed by 2013. In this paper, four transient accidents were simulated for both the critical and sub-critical reactors above by NTC-2D code, which is developed by FDS Team for advanced reactor safety analysis. The four accidents were protected and unprotected loss of heat sink accidents (PLOHS and ULOHS), protected and unprotected transient overpower accidents (PTOP and UTOP). The simulation results of the two reactors were compared and analyzed. The results showed that during PLOHS and PTOP accidents for both the two modes, all the key parameters (core power, fuel, cladding and coolant temperatures in the hottest channel) decreased to very small values after the reactor scrammed, which meant the reactors under the two modes were both safe. For ULOHS, the fuel, cladding and coolant temperatures of the sub-critical reactor increased bigger than those of the critical one. For UTOP, the parameters above of the critical fast reactor were much bigger than those of the sub-critical one. The analysis results showed different safety advantages of the lead-based critical fast and sub-critical reactors during different transient accidents. (author)

A study of physics of sub-critical multiplicative systems driven by sources and the utilization of deterministic codes in calculation of this systems

International Nuclear Information System (INIS)

Antunes, Alberi

2008-01-01

This work presents the Physics of Source Driven Systems (ADS). It shows some statics and K i netics parameters of the reactor Physics and when it is sub critical, that are important in evaluation and definition of these systems. The objective is to demonstrate that there are differences in parameters when the reactor is critical. Moreover, the work shows the differences observed in the parameters for different calculation models. Two calculation methodologies are shown In this dissertation: Gandini and Salvatores and Dulla, and some parameters are calculated. The ANISN deterministic transport code is used in calculation in order to compare these parameters. In a subcritical configuration of IPEN-MB-01 Reactor driven by an external source some parameters are calculated. The conclusions about calculation realized are presented in end of work. (author)

Fusion-driven sub-critical dual-cooled waste transmutation blanket: design and analysis

International Nuclear Information System (INIS)

Wang Weihua; Wu Yican; Ke Yan; Kang Zhicheng; Wang Hongyan; Huang Qunying

2003-01-01

The Fusion-Driven Sub-critical System (FDS) is one of the Chinese programs to be further developed for fusion application. Its Dual-cooled Waste Transmutation Blanket (DWTB), as one the most important part of the FDS is cooled by helium and liquid metal, and have the features of safety, tritium self-sustaining, high efficiency and feasibility. Its conceptual design has been finished. This paper is mainly involved with the basic structure design and thermal-hydraulics analysis of DWTB. On the basis of a three-dimensional (3-D) model of radial-toroidal sections of the segment box, thermal temperature gradients and structure analysis made with a comprehensive finite element method (FEM) have been performed with the computer code ANSYS5.7 and computational fluid dynamic finite element codes. The analysis refers to the steady-state operating condition of an outboard blanket segment. Furthermore, the mechanical loads due to coolant pressure in normal operating conditions have been also taken into account. All the above loads have been combined as an input for a FEM stress analysis and the resulting stress distribution has been evaluated. Finally, the structure design and Pb-17Li flow velocity has been optimized according to the calculations and analysis

Assessments of the kinetic and dynamic transient behavior of sub-critical systems (ADS) in comparison to critical reactor systems

International Nuclear Information System (INIS)

Schikorr, W.M.

2001-01-01

The neutron kinetic and the reactor dynamic behavior of Accelerator Driven Systems (ADS) is significantly different from those of conventional power reactor systems currently in use for the production of power. It is the objective of this study to examine and to demonstrate the intrinsic differences of the kinetic and dynamic behavior of accelerator driven systems to typical plant transient initiators in comparison to the known, kinetic and dynamic behavior of critical thermal and fast reactor systems. It will be shown that in sub-critical assemblies, changes in reactivity or in the external neutron source strength lead to an asymptotic power level essentially described by the instantaneous power change (i.e. prompt jump). Shutdown of ADS operating at high levels of sub-criticality, (i.e. k eff ∼0.99), without the support of reactivity control systems (such as control or safety rods), may be problematic in case the ability of cooling of the core should be impaired (i.e. loss of coolant flow). In addition, the dynamic behavior of sub-critical systems to typical plant transients such as protected or unprotected loss of flow (LOF) or heat sink (LOH) transients are not necessarily substantially different from the plant dynamic behavior of critical systems if the reactivity feedback coefficients of the ADS design are unfavorable. As expected, the state of sub-criticality and the temperature feedback coefficients, such as Doppler and coolant temperature coefficient, play dominant roles in determining the course and direction of plant transients. Should the combination of these safety coefficients be very unfavorable, not much additional margin in safety may be gained by making a critical system only sub-critical (i.e. k eff ∼0.95). A careful optimization procedure between the selected operating level of sub-criticality, the safety reactivity coefficients and the possible need for additional reactivity control systems seems, therefore, advisable during the early

Experimental study on neutronics in bombardment of thick targets by high energy proton beams for accelerator-driven sub-critical system

CERN Document Server

Guo Shi Lun; Shi Yong Qian; Shen Qing Biao; Wan Jun Sheng; Brandt, R; Vater, P; Kulakov, B A; Krivopustov, M I; Sosnin, A N

2002-01-01

The experimental study on neutronics in the target region of accelerator-driven sub-critical system is carried out by using the high energy accelerator in Joint Institute for Nuclear Research, Dubna, Russia. The experiments with targets U(Pb), Pb and Hg bombarded by 0.533, 1.0, 3.7 and 7.4 GeV proton beams show that the neutron yield ratio of U(Pb) to Hg and Pb to Hg targets is (2.10 +- 0.10) and (1.76 +- 0.33), respectively. Hg target is disadvantageous to U(Pb) and Pb targets to get more neutrons. Neutron yield drops along 20 cm thick targets as the thickness penetrated by protons increases. The lower the energy of protons, the steeper the neutron yield drops. In order to get more uniform field of neutrons in the targets, the energy of protons from accelerators should not be lower than 1 GeV. The spectra of secondary neutrons produced by different energies of protons are similar, but the proportion of neutrons with higher energy gradually increases as the proton energy increases

Status of intense permanent magnet proton source for China-accelerator driven sub-critical system Linac.

Science.gov (United States)

Wu, Q; Ma, H Y; Yang, Y; Sun, L T; Zhang, X Z; Zhang, Z M; Zhao, H Y; He, Y; Zhao, H W

2016-02-01

Two compact intense 2.45 GHz permanent magnet proton sources and their corresponding low energy beam transport (LEBT) system were developed successfully for China accelerator driven sub-critical system in 2014. Both the proton sources operate at 35 kV potential. The beams extracted from the ion source are transported by the LEBT, which is composed of two identical solenoids, to the 2.1 MeV Radio-Frequency Quadrupole (RFQ). In order to ensure the safety of the superconducting cavities during commissioning, an electrostatic-chopper has been designed and installed in the LEBT line that can chop the continuous wave beam into a pulsed one. The minimum width of the pulse is less than 10 μs and the fall/rise time of the chopper is about 20 ns. The performance of the proton source and the LEBT, such as beam current, beam profile, emittance and the impact to RFQ injection will be presented.

Status of intense permanent magnet proton source for China-accelerator driven sub-critical system Linac

Science.gov (United States)

Wu, Q.; Ma, H. Y.; Yang, Y.; Sun, L. T.; Zhang, X. Z.; Zhang, Z. M.; Zhao, H. Y.; He, Y.; Zhao, H. W.

2016-02-01

Two compact intense 2.45 GHz permanent magnet proton sources and their corresponding low energy beam transport (LEBT) system were developed successfully for China accelerator driven sub-critical system in 2014. Both the proton sources operate at 35 kV potential. The beams extracted from the ion source are transported by the LEBT, which is composed of two identical solenoids, to the 2.1 MeV Radio-Frequency Quadrupole (RFQ). In order to ensure the safety of the superconducting cavities during commissioning, an electrostatic-chopper has been designed and installed in the LEBT line that can chop the continuous wave beam into a pulsed one. The minimum width of the pulse is less than 10 μs and the fall/rise time of the chopper is about 20 ns. The performance of the proton source and the LEBT, such as beam current, beam profile, emittance and the impact to RFQ injection will be presented.

Status of intense permanent magnet proton source for China-accelerator driven sub-critical system Linac

Energy Technology Data Exchange (ETDEWEB)

Wu, Q., E-mail: wuq@impcas.ac.cn; Ma, H. Y.; Yang, Y.; Sun, L. T.; Zhang, X. Z.; Zhang, Z. M.; Zhao, H. Y.; He, Y.; Zhao, H. W. [Institute of Modern Physics (IMP), Chinese Academy of Sciences, Lanzhou 730000 (China)

2016-02-15

Two compact intense 2.45 GHz permanent magnet proton sources and their corresponding low energy beam transport (LEBT) system were developed successfully for China accelerator driven sub-critical system in 2014. Both the proton sources operate at 35 kV potential. The beams extracted from the ion source are transported by the LEBT, which is composed of two identical solenoids, to the 2.1 MeV Radio-Frequency Quadrupole (RFQ). In order to ensure the safety of the superconducting cavities during commissioning, an electrostatic-chopper has been designed and installed in the LEBT line that can chop the continuous wave beam into a pulsed one. The minimum width of the pulse is less than 10 μs and the fall/rise time of the chopper is about 20 ns. The performance of the proton source and the LEBT, such as beam current, beam profile, emittance and the impact to RFQ injection will be presented.

Analysis of neutronics and dynamic characteristics with reactivity injection in LBE cooled sub-critical reactor

International Nuclear Information System (INIS)

Chen Sen; Wu Yican; Jin Ming; Chen Zhibin; Bai Yunqing; Zhao Zhumin

2014-01-01

Accelerator Driven Sub-critical System (ADS) has particular neutronics behaviors compared with the critical system. Prompt jump approximation point reactor kinetics equations taken external source into account have been deduced using an approach of prompt jump approximation. And the relationship between injection reactivity and power ampliation has been achieved. In addition, based on the RELAP5 code the prolong development of point reactor kinetics code used into assessing sub-critical system have been promoted. Different sub-criticality (k eff = 0.90, 0.95, 0.97, 0.98 and 0.99) have been assessed in preliminary design of a type of natural circulation cooling sub-critical reactor under conditions of reactivity injection +1 β in one second. It shows that the external source prompt transient approximation method has an accurate solution after injecting reactivity around short time and has a capacity to solve the dynamic equation, and the sub-critical system has an inner stability while the deeper sub-criticality the less impact on the sub-critical system. (authors)

Proposed sub-criticality level for an 80 MWTHd-bismuth-cooled Ads

International Nuclear Information System (INIS)

Mansani, L.; Monti, R.; Neuhold, P.

2003-01-01

The degree of operational sub-criticality of an Accelerator-driven System (ADS) on the one hand directly affects key accelerator system parameters, such as the proton beam current required to sustain the selected rated power level and, on the other, the likelihood of approaching or attaining criticality under abnormal or accident conditions. Then, if in all such conditions the safety goal is pursued to design the sub-critical core so that it stays away from criticality with adequate margin, the required operational sub-criticality level must be determined by a properly balanced approach between excessively demanding accelerator system performances and risk of accidental criticality. The approach must necessarily include evaluation and appropriate combination of the relevant reactivity effects (e.g. from system cool-down, postulated accident scenarios, geometrical variations) and proper consideration of specific design features (such as, for instance, the absence of safety rods, intended as neutron absorbing devices having a role equivalent to the shutdown rods in critical reactors). The paper presents a possible approach to the determination of the operational sub-criticality level of an 80 MWth Lead-Bismuth-cooled pool type ADS, initially conceived and developed by a team of Italian Organisations led by Ansaldo, with funding from the Ministry of University and Scientific and Technological Research, and currently in the process of being assessed, versus a gas-cooled concept, in the frame of a contract with the Commission of the European Communities. After a brief description of the Lead-Bismuth-cooled ADS concept relevant features and of the key safety goals in terms of required sub-criticality margin, the evaluated reactivity effects are presented, a method to combine them is discussed and a proposed operational sub-criticality level is derived. (author)

Hybridized Kibble-Zurek scaling in the driven critical dynamics across an overlapping critical region

Science.gov (United States)

Zhai, Liang-Jun; Wang, Huai-Yu; Yin, Shuai

2018-04-01

The conventional Kibble-Zurek scaling describes the scaling behavior in the driven dynamics across a single critical region. In this paper, we study the driven dynamics across an overlapping critical region, in which a critical region (Region A) is overlaid by another critical region (Region B). We develop a hybridized Kibble-Zurek scaling (HKZS) to characterize the scaling behavior in the driven process. According to the HKZS, the driven dynamics in the overlapping region can be described by the critical theories for both Region A and Region B simultaneously. This results in a constraint on the scaling function in the overlapping critical region. We take the quantum Ising chain in an imaginary longitudinal field as an example. In this model, the critical region of the Yang-Lee edge singularity and the critical region of the ferromagnetic-paramagnetic phase transition overlap with each other. We numerically confirm the HKZS by simulating the driven dynamics in this overlapping critical region. The HKZSs in other models are also discussed.

Consultancy on the potential of fusion/fission sub-critical neutron systems for energy production and transmutation. Working material

International Nuclear Information System (INIS)

2005-01-01

The Workshop on Sub-critical Neutron Production held at the University of Maryland and the Eisenhower Institute on 11-13 October 2004 brought together members of fusion, fission and accelerator technical communities to discuss issues of spent fuel, nonproliferation, reactor safety and the use of neutrons for sub-critical operation of nuclear reactors. The Workshop strongly recommended that the fusion community work closely with other technical communities to ensure that a wider range of technical solutions is available to solve the spent fuel problem and to utilize the current actinide inventories. Participants of the Workshop recommended that a follow-on Workshop, possibly under the aegis of the IAEA, should be held in the first half of the year 2005. The Consultancy Meeting is the response to this recommendation. The objectives of the Consultancy meeting were to hold discussions on the role of fusion/fission systems in sub-critical operations of nuclear reactors. The participants agreed that development of innovative (fourth generation) fission reactors, advanced fuel cycle options, and disposition of existing spent nuclear fuel inventories in various Member Sates can significantly benefit from including sub-critical systems, which are driven by external neutron sources. Spallation neutrons produced by accelerators have been accepted in the past as the means of driving sub-critical reactors. The accelerator community deserves credit in pioneering this novel approach to reactor design. Progress in the design and operation of fusion devices now offers additional innovative means, broadening the range of sub-critical operations of fission reactors. Participants felt that fusion should participate with accelerators in providing a range of technical options in reactor design. Participants discussed concrete steps to set up a small fusion/fission system to demonstrate actinide burning in the laboratory and what advice should be given to the Agency on its role in

Critical current anisotropy in Ag/(Pb,Bi){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10+x} multifilamentary tapes: influence of self-magnetic field

Energy Technology Data Exchange (ETDEWEB)

Majoros, M [IRC in Superconductivity, University of Cambridge, Cambridge (United Kingdom); Institute of Electrical Engineering, Slovak Academy of Sciences, Bratislava (Slovakia); Glowacki, B A [IRC in Superconductivity, University of Cambridge, Cambridge (United Kingdom); Department of Materials Science and Metallurgy, University of Cambridge, Cambridge (United Kingdom); Campbell, A M [IRC in Superconductivity, University of Cambridge, Cambridge (United Kingdom)

2001-06-01

Two factors affect critical current anisotropy in multifilamentary Ag/(Pb,Bi){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10+x} tapes - the intrinsic material anisotropy and the geometry. Experimental results on the magnetic field dependence and anisotropy of the critical current in a multifilamentary Ag/(Pb,Bi){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10+x} tape after correction for self-magnetic field effects were found to fit the anisotropic Kim relation. Based on this relation a finite-element-method numerical code for solving the nonlinear Poisson equation for vector magnetic potential was adopted. It allowed the experimental data to be reproduced by back calculation and made possible the study of the interplay of self and external magnetic fields in different cases with well defined physical parameters of the material. The model was used to analyse the distribution of the critical current in individual filaments as well as to evaluate the influence of their geometrical arrangements on the critical current of the tape. The self-field critical current of an individual filament 'extracted' from the tape was compared with the critical current of the overall tape. The effect of the self-magnetic field on critical current distribution obtained by the cutting method was determined. The critical currents of the tapes with different cross sections were calculated and compared with experiments and the influence of the self-field was analysed. The anisotropic properties of a low anisotropy architecture of a multifilamentary Ag/(Pb,Bi){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10+x} conductor were studied. The dependence of critical currents (normalized to self-field critical currents) on external magnetic field corrected for the self-field was found to follow nearly the same curves as those for tapes with different critical current densities (in the range 20-70 kA cm{sup -2} in a self-field), which makes the numerical model applicable to different tapes. (author)

YALINA facility a sub-critical Accelerator- Driven System (ADS) for nuclear energy research facility description and an overview of the research program (1997-2008).

Energy Technology Data Exchange (ETDEWEB)

Gohar, Y.; Smith, D. L.; Nuclear Engineering Division

2010-04-28

The YALINA facility is a zero-power, sub-critical assembly driven by a conventional neutron generator. It was conceived, constructed, and put into operation at the Radiation Physics and Chemistry Problems Institute of the National Academy of Sciences of Belarus located in Minsk-Sosny, Belarus. This facility was conceived for the purpose of investigating the static and dynamic neutronics properties of accelerator driven sub-critical systems, and to serve as a neutron source for investigating the properties of nuclear reactions, in particular transmutation reactions involving minor-actinide nuclei. This report provides a detailed description of this facility and documents the progress of research carried out there during a period of approximately a decade since the facility was conceived and built until the end of 2008. During its history of development and operation to date (1997-2008), the YALINA facility has hosted several foreign groups that worked with the resident staff as collaborators. The participation of Argonne National Laboratory in the YALINA research programs commenced in 2005. For obvious reasons, special emphasis is placed in this report on the work at YALINA facility that has involved Argonne's participation. Attention is given here to the experimental program at YALINA facility as well as to analytical investigations aimed at validating codes and computational procedures and at providing a better understanding of the physics and operational behavior of the YALINA facility in particular, and ADS systems in general, during the period 1997-2008.

Design status and future research programme for a sub-critical assembly driven by a proton accelerator with proton energy 660 MeV for experiments on long-lived fission products and minor actinides transmutation (Sad)

International Nuclear Information System (INIS)

Gustov, S.A.; Mirokhin, I.V.; Morozov, N.A.; Onischenko, L.M.; Savchenko, O.V.; Sissakian, A.N.; Shvetsov, V.N.; Tretyakov, I.T.; Lopatkin, A.V.; Vorontsov, M.T.

2003-01-01

Report presents project for the construction of a low power integral system on the basis of the proton accelerator of energy 660 MeV and sub-critical MOX blanket with uranium-plutonium fuel. Installation includes sub-critical core with a nominal thermal power of 15-20 kW. Multiplication coefficient k eff = 0,95 and the accelerator beam power of 0.75-1 kW. The experimental programme for SAD will be focused on solving different aspects of reactor physics, reaction rates measurements and benchmarking. The first conceptual design of the SAD experiment is completed in the form of the ISTC Project Proposal 2267. Realisation of the SAD facility may be expected in about 3-4 years. (author)

The mechanical design and fabrication of 162.5 MHz buncher for China accelerator driven sub-critical system injector II

Energy Technology Data Exchange (ETDEWEB)

Niu, Hai Hua; Li, Youtang [Lanzhou University of Technology, Lanzhou (China); He, Yuan; Zhang, Bin; Huang, Shichun; Yuan, Chenzhang; Jia, Huan; Zhang, Shenghu [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou (China)

2017-08-15

A buncher is one of the main pieces of equipment in the medium energy beam transport line (MEBT) for China accelerator driven sub-critical system (C-ADS) Injector II. To focus the beam longitudinally and match the beam for the acceptance of the superconducting linac section, two room temperature quarter wave resonator (QWR) bunchers with frequency of 162.5 MHz have been designed as parts of the MEBT. According to the beam transmission matching of the MEBT and the geometric parameters requirements of bunchers, the unique mechanical structure and the main processing technology of buncher cavities and their couplers and tuners are described in this paper. The fabrication of bunchers and their parts have been completed and tested at high power, the test results agree well with the design requirements. These bunchers work well for about two years in Institute of Modern Physics, Chinese Academy of Sciences.

Results of 16 years' experiments at the critical facility of Valduc

International Nuclear Information System (INIS)

Houelle, M.; Mangin, D.; Maubert, L.

After briefly recalling the sub-critical approach procedure, the fields of experimental studies on criticality explored at the Valduc Criticality Station since 1963 are listed. This was the year in which the ''appareillage B'' went into service as the first installation of sub-critical experiments of the Section [fr

The physics of accelerator driven sub-critical reactors

Indian Academy of Sciences (India)

Accelerator driven systems (ADS) are attracting worldwide attention .... The region of interest (or the entire reactor core) is divided into a suitable number ..... have also presented the status of the theoretical and experimental activities being.

Infield X-ray diffraction studies of field and temperature driven structural phase transition in Nd{sub 0.49}Sr{sub 0.51}MnO{sub 3+δ}

Energy Technology Data Exchange (ETDEWEB)

Shahee, Aga, E-mail: agashahee@gmail.com [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001 (India); Department of Physics, IIT Bombay, Powai, Mumbai 400076 (India); Sharma, Shivani; Singh, K.; Lalla, N.P. [UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452001 (India)

2017-07-15

Highlights: • Temperature and magnetic field driven coupled magneto-structural phase transition in Nd{sub 0.49}Sr{sub 0.51}MnO{sub 3+δ}. • Microscopic evidence of strong spin-charge-lattice coupling. • Iso-thermal magnetic field driven structure phase transition. • Field-driven structural phase transition origin of observed 1st order type CMR effect. - Abstract: Comprehensive X-ray diffraction (XRD) studies have been performed at different temperature (T) (4.2–300 K) and magnetic field (H) (0–8 T) to understand the evolution of crystal structure of Nd{sub 0.49}Sr{sub 0.51}MnO{sub 3+δ} (NSMO) under non ambient conditions. The T dependent XRD results show the abrupt change in the lattice parameters without any change in lattice symmetry at ∼200 K, which is associated with the first order structural phase transition from ferromagnetic to antiferromagnetic phase. This phase transition is strongly H dependent and shifted to lower temperature (∼150 K) on the application of 8 T field with phase coexistence (high temperature phase ∼18%), even down to 4.2 K. Isothermal XRD results at 150 K under different H clearly illustrate the H induced first order structural phase transition. The critical H at which this phase transformation starts is ∼1 T, with rapid growth above 4 T with hysteretic nature during increasing and decreasing H. These results are supported with the resistivity and magnetoresistance results and affirm the strong spin-lattice coupling in NSMO. Our detail studies reveal the structural correlations to the observed colossal magnetoresistance and magnetocaloric effect in this material.

Accelerator-driven sub-critical target concept for transmutation of nuclear wastes

International Nuclear Information System (INIS)

Van Tuyle, G.J.; Todosow, M.; Aronson, A.L.; Takahashi, H.; Geiger, M.J.

1991-01-01

A means of transmuting key long-lived nuclear wastes, primarily the minor actinides (Np, Am, Cm) and iodine, using a hybrid proton accelerator and sub-critical lattice, is proposed. By partitioning the components of the light water reactor (LWR) spent fuel and by transmuting key elements, such as the plutonium, the minor actinides, and a few of the long-lived fission products, some of the most significant challenges in building a waste repository can be substantially reduced. The proposed machine, based on the described PHOENIX Concept, would transmute the minor actinides and the iodine produced by 75 LWRs, and would generate usable electricity (beyond that required to run the large accelerator) of 850 MW e . 19 refs., 20 figs

Correlations between critical current density, j{sub c}, critical temperature, T{sub c}, and structural quality of Y{sub 1}B{sub 2}Cu{sub 3}O{sub 7-x} thin superconducting films

Energy Technology Data Exchange (ETDEWEB)

Chrzanowski, J.; Xing, W.B.; Atlan, D. [Simon Fraser Univ., British Columbia (Canada)] [and others

1994-12-31

Correlations between critical current density (j{sub c}) critical temperature (T{sub c}) and the density of edge dislocations and nonuniform strain have been observed in YBCO thin films deposited by pulsed laser ablation on (001) LaAlO{sub 3} single crystals. Distinct maxima in j{sub c} as a function of the linewidths of the (00{ell}) Bragg reflections and as a function of the mosaic spread have been found in the epitaxial films. These maxima in j{sub c} indicate that the magnetic flux lines, in films of structural quality approaching that of single crystals, are insufficiently pinned which results in a decreased critical current density. T{sub c} increased monotonically with improving crystalline quality and approached a value characteristic of a pure single crystal. A strong correlation between j{sub c} and the density of edge dislocations N{sub D} was found. At the maximum of the critical current density the density of edge dislocations was estimated to be N{sub D}{approximately}1-2 x 10{sup 9}/cm{sup 2}.

The mechanical design and fabrication of 162.5 MHz buncher for China accelerator driven sub-critical system injector II

Directory of Open Access Journals (Sweden)

Haihua Niu

2017-08-01

Full Text Available A buncher is one of the main pieces of equipment in the medium energy beam transport line (MEBT for China accelerator driven sub-critical system (C-ADS Injector II. To focus the beam longitudinally and match the beam for the acceptance of the superconducting linac section, two room temperature quarter wave resonator (QWR bunchers with frequency of 162.5 MHz have been designed as parts of the MEBT. According to the beam transmission matching of the MEBT and the geometric parameters requirements of bunchers, the unique mechanical structure and the main processing technology of buncher cavities and their couplers and tuners are described in this paper. The fabrication of bunchers and their parts have been completed and tested at high power, the test results agree well with the design requirements. These bunchers work well for about two years in Institute of Modern Physics, Chinese Academy of Sciences.

Numerical Analysis of S-CO{sub 2} Test Loop Transient Conditions near the Critical Point of CO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Bae, Seong Jun; Oh, Bongseong; Ahn, Yoonhan; Baik, Seongjoon; Lee, Jekyoung; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of)

2016-05-15

It was identified that controlling CO{sub 2} compressor operation near the critical point is one of the most important issues to operate a S-CO{sub 2} Brayton cycle with a high efficiency. Despite the growing interest in the S-CO{sub 2} Brayton cycle, a few previous research on the transient analysis of the S-CO{sub 2} system has been conducted previously. Moreover, previous studies have some limitation in the modelled test facility, and the experiment was not performed to observe specific scenario. The KAIST research team has conducted S-CO{sub 2} system transient experiments with the CO{sub 2} compressing test facility called SCO{sub 2}PE (Supercritical CO{sub 2} Pressurizing Experiment) at KAIST In this study, authors use the transient analysis code GAMMA (Gas Multidimensional Multicomponent mixture Analysis) code for analyzing the experiment. Two transient scenarios were selected in this study; over cooling and under cooling situations. The selected transient situation is of particular interest since the compressor inlet conditions start to drift away from the critical point of CO{sub 2}. The results represent that the GAMMA code can simulate the S-CO{sub 2} test facility, SCO{sub 2}PE. However, as shown in the cooling water flow rate increasing scenario, the GAMMA code shows calculation error when the phase change occurs. Furthermore, although the results of the cooling water flow rate decrease case shows reasonable agreement with the experimental data, there are still some unexplained differences between the experimental data and the GAMMA code prediction.

Critical currents of Y sub 1 Ba sub 2 Cu sub 3 O sub 7-. delta. ceramics

Energy Technology Data Exchange (ETDEWEB)

Vasiliev, B V; Obukhov, Yu V [Joint Inst. for Nuclear Research, Low Temperature Physics Dept., Moscow (USSR)

1991-12-01

The magnetization measurements on a ceramic YBaCuO sample were carried out. The M(H,T) dependence has demonstrated some peculiarities which we suppose to be connected with H{sub j1}, H{sub j2}, H{sub C1} fields. By analizing the magnetization in the field region between H{sub j1} and H{sub j2} within the frame of the critical state model one can found the dependence of the intergranular critical current density on field and temperature. (orig.).

Preparation of K-doped TiO{sub 2} nanostructures by wet corrosion and their sunlight-driven photocatalytic performance

Energy Technology Data Exchange (ETDEWEB)

Shin, Eunhye; Jin, Saera; Kim, Jiyoon; Chang, Sung-Jin [Department of Chemistry, Chung-Ang University, Seoul 06974 (Korea, Republic of); Jun, Byung-Hyuk [Neutron Science Division, Korea Atomic Energy Research Institute, Daejeon 34057 (Korea, Republic of); Park, Kwang-Won, E-mail: bryan.kwangwon.park@gmail.com [Department of Chemistry, Chung-Ang University, Seoul 06974 (Korea, Republic of); Hong, Jongin, E-mail: hongj@cau.ac.kr [Department of Chemistry, Chung-Ang University, Seoul 06974 (Korea, Republic of)

2016-08-30

Highlights: • Potassium-doped TiO{sub 2} nanowire networks were prepared by the corrosion reaction of Ti nanoparticles in an alkaline solution. • They were applied to sunlight-driven photocatalytic degradation of differently charged dye molecules. • The adsorption of the dye molecules on the photocatalyst surface is crucial for their sunlight-driven photodegradation. - Abstract: K-doped TiO{sub 2} nanowire networks were prepared by the corrosion reaction of Ti nanoparticles in an alkaline (potassium hydroxide: KOH) solution. The prepared nanostructures were characterized by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) analysis, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, X-ray diffraction (XRD) and photoluminescence (PL) spectra. Their sunlight-driven photocatalytic activity was also investigated with differently charged dye molecules, such as methylene blue, rhodamine B and methyl orange. The adsorption of the dye molecules on the photocatalyst surface would play a critical role in their selective photodegradation under sunlight illumination.

Quasi-monoenergetic ion beam acceleration by laser-driven shock and solitary waves in near-critical plasmas

Energy Technology Data Exchange (ETDEWEB)

Zhang, W. L.; Qiao, B., E-mail: bqiao@pku.edu.cn; Huang, T. W.; Shen, X. F.; You, W. Y. [Center for Applied Physics and Technology, HEDPS, and State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, Shanxi 030006 (China); Yan, X. Q. [Center for Applied Physics and Technology, HEDPS, and State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Wu, S. Z. [Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China); Zhou, C. T.; He, X. T. [Center for Applied Physics and Technology, HEDPS, and State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871 (China); Institute of Applied Physics and Computational Mathematics, Beijing 100094 (China)

2016-07-15

Ion acceleration in near-critical plasmas driven by intense laser pulses is investigated theoretically and numerically. A theoretical model has been given for clarification of the ion acceleration dynamics in relation to different laser and target parameters. Two distinct regimes have been identified, where ions are accelerated by, respectively, the laser-induced shock wave in the weakly driven regime (comparatively low laser intensity) and the nonlinear solitary wave in the strongly driven regime (comparatively high laser intensity). Two-dimensional particle-in-cell simulations show that quasi-monoenergetic proton beams with a peak energy of 94.6 MeV and an energy spread 15.8% are obtained by intense laser pulses at intensity I{sub 0} = 3 × 10{sup 20 }W/cm{sup 2} and pulse duration τ = 0.5 ps in the strongly driven regime, which is more advantageous than that got in the weakly driven regime. In addition, 233 MeV proton beams with narrow spread can be produced by extending τ to 1.0 ps in the strongly driven regime.

CLUMPED LIGHT WATER MODERATED UO$sub 2$ SUPERHEAT CRITICALS. PART I. EXPERIMENTS

Energy Technology Data Exchange (ETDEWEB)

Warzek, F. G.; Johnston, H. F.

1963-11-15

The following critical and subcritical measurements were made in the EVESR core: reactivity with no control rods; full core reactivity with control rods; and power distribution in the full core with control rods. The fuel was UO/ sub 2/, and the elements were of the superheating type. The reactor was light- water-cooled and -moderated. (T.F.H.)

Angular dependence of the upper critical field in Bi sub 2 Sr sub 2 CuO sub 6 sub + subdelta

CERN Document Server

Vedeneev, S I

2002-01-01

The angular dependence of the upper critical field has been investigated in a wide range of temperatures in very high-quality Bi sub 2 Sr sub 2 CuO sub 6 sub + subdelta single crystals with critical temperature approx = 9 K in magnetic fields up to 28 T. Although the typical value of the normal state resistivity ratio approx = 10 sup 4 , the anisotropy ratio of the upper critical fields is much smaller. A model is proposed based on a strong anisotropy and a small transparency between superconducting layers

Validation of KENO V.a: Comparison with critical experiments

International Nuclear Information System (INIS)

Jordan, W.C.; Landers, N.F.; Petrie, L.M.

1986-12-01

Section 1 of this report documents the validation of KENO V.a against 258 critical experiments. Experiments considered were primarily high or low enriched uranium systems. The results indicate that the KENO V.a Monte Carlo Criticality Program accurately calculates a broad range of critical experiments. A substantial number of the calculations showed a positive or negative bias in excess of 1 1/2% in k-effective (k/sub eff/). Classes of criticals which show a bias include 3% enriched green blocks, highly enriched uranyl fluoride slab arrays, and highly enriched uranyl nitrate arrays. If these biases are properly taken into account, the KENO V.a code can be used with confidence for the design and criticality safety analysis of uranium-containing systems. Sections 2 of this report documents the results of investigation into the cause of the bias observed in Sect. 1. The results of this study indicate that the bias seen in Sect. 1 is caused by code bias, cross-section bias, reporting bias, and modeling bias. There is evidence that many of the experiments used in this validation and in previous validations are not adequately documented. The uncertainty in the experimental parameters overshadows bias caused by the code and cross sections and prohibits code validation to better than about 1% in k/sub eff/. 48 refs., 19 figs., 19 tabs

Transport simulations of ohmic TFTR experiments with profile-consistent microinstability-based models for chi/sub e/ and chi/sub i/

International Nuclear Information System (INIS)

Redi, M.H.; Tang, W.M.; Efthimion, P.C.; Mikkelsen, D.R.; Schmidt, G.L.

1987-03-01

Transport simulations of ohmically heated TFTR experiments with recently developed profile-consistent microinstability models for the anomalous thermal diffusivities, chi/sub e/ and chi/sub i/, give good agreement with experimental data. The steady-state temperature profiles and the total energy confinement times, tau/sub e/, were found to agree for each of the ohmic TFTR experiments simulated, including three high radiation cases and two plasmas fueled by pellet injection. Both collisional and collisionless models are tested. The trapped-electron drift wave microinstability model results are consistent with the thermal confinement of large plasma ohmic experiments on TFTR. We also find that transport due to the toroidal ion temperature gradient (eta/sub i/) modes can cause saturation in tau/sub E/ at the highest densities comparable to that observed on TFTR and equivalent to a neoclassical anomaly factor of 3. Predictions based on stabilized eta/sub i/-mode-driven ion transport are found to be in agreement with the enhanced global energy confinement times for pellet-fueled plasmas. 33 refs., 26 figs., 4 tabs

Development of reactivity feedback effect measurement techniques under sub-critical condition in fast reactors

International Nuclear Information System (INIS)

Kitano, A.; Nishi, H.; Suzuki, T.; Okajima, S.; Kanemoto, S.

2012-01-01

The first-of-a-kind reactor has been licensed by a safety examination of the plant design based on the measured data in precedent mock-up experiments. The validity of the safety design can be confirmed without a mock-up experiment, if the reactor feed-back characteristics can be measured before operation, with the constructed reactor itself. The 'Synthesis Method', a systematic and sophisticated method of sub-criticality measurement, is proposed in this work to ensure the safety margin before operation. The 'Synthesis Method' is based on the modified source multiplication method (MSM) combined with the noise analysis method to measure the reference sub-criticality level for MSM. A numerical simulation for the control-rod reactivity worth and the isothermal feed-back reactivity was conducted for typical fast reactors of 100 MWe-size, 300 MWe-size, 750 MWe-size, and 1500 MWe-size to investigate the applicability of Synthesis Method. The number of neutron detectors and their positions necessary for the measurement were investigated for both methods of MSM and the noise analysis by a series of parametric survey calculations. As a result, it was suggested that a neutron detector located above the core center and three or more neutron detectors located above the radial blanket region enable the measurement of sub-criticality within 10% uncertainty from -$0.5 to -$2 and within 15% uncertainty for the deeper sub-criticality. (authors)

Electron heating caused by parametrically driven turbulence near the critical density

International Nuclear Information System (INIS)

Mizuno, K.; DeGroot, J.S.; Estabrook, K.G.

1986-01-01

Microwave-driven experiments and particle simulation calculations are presented that model s-polarized laser light incident on a pellet. In the microwave experiments, the incident microwaves are observed to decay into ion and electron waves near the critical density if the microwave power is above a well-defined threshold. Significant absorption, thermal electron heating, and hot electron generation are observed for microwave powers above a few times threshold. Strong absorption, strong profile modification, strongly heated hot electrons with a Maxwellian distribution, a hot-electron temperature that increases slowly with power, and a hot-electron density that is almost constant, are all observed in both the microwave experiments and simulation calculations for high powers. In addition, the thermal electrons are strongly heated for high powers in the microwave experiments

Critical radius and critical number of gas atoms for cavities containing a Van der Waals gas

International Nuclear Information System (INIS)

Coghlan, W.A.; Mansur, L.K.

1983-01-01

The effect of gas on void nucleation and growth is particularly important for structural materials in fusion reactors because of the high production of helium by neutron-induced transmutation reactions. Gas reduces the critical radius for bias driven growth and there is a critical number of gas atoms, n/sub g/*, at which the critical radius is reduced essentially to zero. The significance of this is that the time interval to the accumulation of n/sub g/* gas atoms may determine the time to the onset of bias driven swelling where n/sub g/* is large. In previous papers these critical quantities were given for an ideal gas. Recently, we presented the results for a Van der Waals gas. Here the derivation of these relations is presented and further results of calculations are given. At low temperatures (high pressures) the results depart from those of the ideal gas, with the critical number affected more strongly than the critical radius. Comparisons are made with earlier calculations

Accelerator Driven Sub-Critical System for the Radioactive Waste Transmutation

International Nuclear Information System (INIS)

Avramovic, I.; Pesic, M.

2008-01-01

Spent nuclear fuel discharged from nuclear power plants is the main problem during design of radioactive waste disposal. Most of the hazard stems from only a few chemical elements. The radiotoxicity of these elements can be efficiently reduced using partitioning and transmutation in fast reactors and accelerator driven subcritical systems. (author)

Superconducting critical state of Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub 8]: two-dimensional effects at low temperatures

Energy Technology Data Exchange (ETDEWEB)

Rodriguez, E. (Comision Nacional de Energia Atomica, Centro Atomico Bariloche (Argentina)); Goffman, M.F. (Comision Nacional de Energia Atomica, Centro Atomico Bariloche (Argentina)); Arribere, A. (Comision Nacional de Energia Atomica, Centro Atomico Bariloche (Argentina)); Cruz, F. de la (Comision Nacional de Energia Atomica, Centro Atomico Bariloche (Argentina)); Schneemeyer, L.F. (AT and T Bell Labs., Murray Hill, NJ (United States))

1994-02-01

The critical current in the c direction of Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub 8] is shown to increase with temperature in low temperature ZFC measurements. The results are consistent with a loss of the c direction long range phase correlation, induced by the temperature dependent critical current flowing in the ab planes. As a result of this and the loss of the long range correlation induced by thermal disorder, the low temperature electrical resistance of the ZFC critical state is finite at low temperatures, becomes zero and is finite again at higher temperature. (orig.)

Experimental and Numerical Analysis of S-CO{sub 2} Critical Flow for SFR Recovery System Design

Energy Technology Data Exchange (ETDEWEB)

Kim, Min Seok; Jung, Hwa-Young; Ahn, Yoonhan; Lee, Jekyoung; Lee, Jeong Ik [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

2016-05-15

This paper presents both numerical and experimental studies of the critical flow of S-CO{sub 2} while special attention is given to the turbo-machinery seal design. A computational critical flow model is described first. The experiments were conducted to validate the critical flow model. Various conditions have been tested to study the flow characteristic and provide validation data for the model. The comparison of numerical and experimental results of S-CO{sub 2} critical flow will be presented. In order to eliminate SWR, a concept of coupling the Supercritical CO{sub 2} (S-CO{sub 2}) cycle with SFR has been proposed. It is known that for a closed system controlling the inventory is important for stable operation and achieving high efficiency. Since the S-CO{sub 2} power cycle is a highly pressurized system, certain amount of leakage flow is inevitable in the rotating turbo-machinery via seals. To simulate the CO{sub 2} leak flow in a turbo-machinery with higher accuracy in the future, the real gas effect and friction factor will be considered for the CO{sub 2} critical flow model. Moreover, experimentally obtained temperature data were somewhat different from the numerically obtained temperature due to the insufficient insulation and large thermal inertia of the CO{sub 2} critical flow facility. Insulation in connecting pipes and the low-pressure tank will be added and additional tests will be conducted.

Critical experiments for large scale enriched uranium solution handling

International Nuclear Information System (INIS)

Tanner, J.E.; Forehand, H.M.

1985-01-01

The authors have performed 17 critical experiments with a concentrated aqueous uranyl nitrate solution contained in an annular cylindrical tank, with annular cylindrical absorbers of stainless steel and/or polyethylene inside. k/sub eff/ calculated by KENO IV, employing 16-group Hansen-Roach cross sections, average 0.977. There is a variation of the calculational bias among the separate experiments, but it is too small to allow assigning it to specific components of the equipment. They are now performing critical experiments with a more concentrated uranyl nitrate solution in pairs of very squat cylindrical tanks with disc shaped absorbers and reflectors of carbon steel, stainless steel, nitronic-50, plain and borated polyethylene. These experiments are in support of upgrading fuel reprocessing at the Idaho Chemical Processing Plant

Optical properties and visible-light-driven photocatalytic activity of Bi{sub 8}V{sub 2}O{sub 17} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Pu, Yinfu; Liu, Ting; Huang, Yanlin [Soochow University, College of Chemistry, Chemical Engineering and Materials Science (China); Chen, Cuili; Kim, Sun Il; Seo, Hyo Jin, E-mail: hjseo@pknu.ac.kr [Pukyong National University, Department of Physics and Interdisciplinary Program of Biomedical, Mechanical & Electrical Engineering (Korea, Republic of)

2015-05-15

Bi{sub 8}V{sub 2}O{sub 17} (4Bi{sub 2}O{sub 3}·V{sub 2}O{sub 5}) nanoparticles with the uniform size of about 50 nm were fabricated through the Pechini method. The crystal structure was investigated by X-ray powder diffraction and the structural refinement. The surface of the as-synthesized samples was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy, and X-ray photoelectron spectroscopy. The optical properties, band structure, and the degradation mechanisms were discussed. The experimental results demonstrate that Bi{sub 8}V{sub 2}O{sub 17} nanoparticles have an efficient visible-light absorption with band-gap energy of 1.85 eV and a direct allowed electronic transition. The photocatalytic activity was evaluated by the photodegradation of the methylene blue (MB) under visible-light irradiation (λ > 420 nm) as a function of time. These results indicate that Bi{sub 8}V{sub 2}O{sub 17} could be a potential photocatalyst driven by visible light. The effective photocatalytic activity was discussed on the base of the crystal structure characteristic.

A visible-light-driven photocatalytic activity of vanadate garnet AgCa{sub 2}Ni{sub 2}V{sub 3}O{sub 12} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Lu, Yuting; Chen, Luyang; Li, Yuze; Huang, Yanlin [Soochow University, College of Chemistry, Chemical Engineering and Materials Science (China); Cheng, Han; Seo, Hyo Jin, E-mail: hjseo@pknu.ac.kr [Pukyong National University, Department of Physics and Interdisciplinary Program of Biomedical, Mechanical and Electrical Engineering (Korea, Republic of)

2015-10-15

A visible-light-driven photocatalyst of nanosized vanadate garnet AgCa{sub 2}Ni{sub 2}V{sub 3}O{sub 12} was prepared by a modified Pechini method. The nanoparticles were characterized with the measurements such as X-ray powder diffraction (XRD) and structural refinements, scanning electron microscope (SEM), and UV–visible (UV–Vis) absorption spectrum. The sample has an efficient absorption in the UV–Vis light region with a narrow band-gap energy of 2.16 eV and an indirect allowed electronic transition. Besides, the photocatalysis of AgCa{sub 2}Ni{sub 2}V{sub 3}O{sub 12} nanoparticles was evaluated by photo-degradation of methylene blue under visible-light irradiation, which shows excellent photocatalytic activity. The effective photocatalytic activity was discussed on the base of the garnet crystal structure such as the activated optical centers of Ni–O octahedron and V–O tetrahedral, highly distorted Ag–O dodecahedra, and long V–V distance in the lattices.

Design of a molten heavy-metal coolant and target for fast-thermal accelerator driven sub-critical system (ADS)

International Nuclear Information System (INIS)

Satyamurthy, P.; Degwekar, S.B.; Nema, P.K.

2001-01-01

Accelerator Driven sub-critical Systems (ADS) have evoked considerable interest in recent years. The Energy Amplifier concept developed by C. Rubbia and others at CERN incorporates a buoyancy driven, lead-coolant primary system for extracting the heat generated in the fast reactor as well as that in neutron spallation target. In earlier publications, our BARC group has proposed a one-way coupled booster reactor system which could be operated at proton beam currents as low as 1-2 mA for a power output of 750 MW th . Here, the basic idea is to have a fast booster reactor zone of low power (- 100 MW th ) which is separated by a large gap from the main thermal reactor zone. In this arrangement, the spallation neutron source feeds neutrons to the fast reactor zone where neutrons are further multiplied. Further in this system, the neutrons from the booster region enter the main reactor but very few neutrons from main reactor return to booster, thus ensuring one-way coupling. In earlier work, several possible configurations of the booster and thermal regions were presented. In the present work, we describe an engineering design particularly with respect to thermal hydraulics of lead/lead-bismuth eutectic coolant also acting as spallation neutron source. This hybrid ADS reactor consists of fast and thermal reactor zones producing about 100 MW th and 650 MW th respectively. The scheme of the system is shown. The fast core consists of 48 hexagonal fuel bundles each containing 169 fuel pins of 8.2 mm diameter arranged in 11.4 mm triangular array pitch. The average thermal power per fuel pin is about 13.46 kw. However, due to neutron flux peaking effect, the maximum fuel pin power can be up to 2.5 times this average power. The thermal reactor consists of heavy water as moderator and coolant similar to a typical CANDU type Indian PHWR except for fuel composition. Though the gap between fast and thermal zones essentially provides one way coupling of neutron flux, a thermal

LaCu<sub>6-xsub>Ag_{x>: A promising host of an elastic quantum critical point}

Energy Technology Data Exchange (ETDEWEB)

Poudel, Lekh [ORNL; Dela Cruz, Clarina R. [ORNL; Koehler, Michael R. [University of Tennessee, Knoxville (UTK); McGuire, Michael A. [ORNL; Keppens, Veerle [University of Tennessee, Knoxville (UTK); Mandrus, David [ORNL; Christianson, Andrew D. [ORNL

2018-05-01

Structural properties of LaCu<sub>6-xsub>Ag<sub>x> have been investigated using neutron and x-ray diffraction, and resonant ultrasound spectroscopy (RUS) measurements. Diffraction measurements indicate a continuous structural transition from orthorhombic (Pnma) to monoclinic (P2₁/C) structure. RUS measurements show softening of natural frequencies at the structural transition, consistent with the elastic nature of the structural ground state. The structural transition temperatures in LaCu<sub>6-xsub>Agx> decrease with Ag composition until the monoclinic phase is completely suppressed at x<sub>c>=0.225. All of the evidence is consistent with the presence of an elastic quantum critical point in LaCu_6-xsub>Agx>.

Estimated critical conditions for UO[sub 2]F[sub 2]--H[sub 2]O systems in fully water-reflected spherical geometry

Energy Technology Data Exchange (ETDEWEB)

Jordan, W.C.; Turner, J.C.

1992-12-01

The purpose of this report is to document reference calculations performed using the SCALE-4.0 code system to determine the critical parameters of UO[sub 2]F[sub 2]-H[sub 2]O spheres. The calculations are an extension of those documented in ORNL/CSD/TM-284. Specifically, the data for low-enriched UO[sub 2]F[sub 2]-H[sub 2]O spheres have been extended to highly enriched uranium. These calculations, together with those reported in ORNL/CSD/TM-284, provide a consistent set of critical parameters (k[sub [infinity

Microstructure and critical current of superconducting YBa/sub 2/Cu/sub 3/Osub(7-x)

Energy Technology Data Exchange (ETDEWEB)

Camps, R A; Evetts, J E; Glowacki, B A; Newcomb, S B; Somekh, R E; Stobbs, W M

1987-09-17

The authors present the main results of a detailed electron microscopical study of sintered YBa/sub 2/Cu/sub 3/0sub(7-x), and discuss their relevance to observed critical current and its modification by increased silicon impurity levels. In the light of these results, the prospects are assessed for controlling microstructure development so as to optimize the critical current for technological application.

On Mixed Data and Event Driven Design for Adaptive-Critic-Based Nonlinear $H_{\\infty}$ Control.

Science.gov (United States)

Wang, Ding; Mu, Chaoxu; Liu, Derong; Ma, Hongwen

2018-04-01

In this paper, based on the adaptive critic learning technique, the control for a class of unknown nonlinear dynamic systems is investigated by adopting a mixed data and event driven design approach. The nonlinear control problem is formulated as a two-player zero-sum differential game and the adaptive critic method is employed to cope with the data-based optimization. The novelty lies in that the data driven learning identifier is combined with the event driven design formulation, in order to develop the adaptive critic controller, thereby accomplishing the nonlinear control. The event driven optimal control law and the time driven worst case disturbance law are approximated by constructing and tuning a critic neural network. Applying the event driven feedback control, the closed-loop system is built with stability analysis. Simulation studies are conducted to verify the theoretical results and illustrate the control performance. It is significant to observe that the present research provides a new avenue of integrating data-based control and event-triggering mechanism into establishing advanced adaptive critic systems.

Critical parameters and saturated density of trifluoroiodomethane (CF{sub 3}I)

Energy Technology Data Exchange (ETDEWEB)

Duan, Y.Y.; Shi, L.; Zhu, M.S.; Han, L.Z. [Tsinghua Univ., Beijing (China). Dept. of Thermal Engineering

1999-05-01

The vapor-liquid coexistence curve of trifluoroiodomethane (CF{sub 3}I) was measured by visual observation of the meniscus disappearance in an optical cell. Thirty-two saturated density data points were obtained along the vapor-liquid coexistence curve between 384.5 and 2024.9 kg/m{sup 3} in the temperature range from 301.02 K to the critical temperature. The experimental uncertainties in temperature and density were estimated to be within {+-}10 mK and {+-}0.5%, respectively. Measurements near the critical point were used to determine the critical temperature T{sub c} = 396.44 {+-} 0.01 K and the critical density {rho}{sub c} = 868 {+-} 3 kg/m{sup 3} for trifluoroiodomethane (CF{sub 3}I) on the basis of the meniscus disappearing level as well as the intensity of the critical opalescence. The critical pressure {rho}{sub c} = 3.953 {+-} 0.005 MPa was extrapolated from the existing vapor pressure equation proposed previously using the present {Tc} value. The critical exponent, {beta}, was also determined, and correlations of the saturated liquid and saturated vapor densities of CF{sub 3}I were developed.

Effect of pelletization pressure on structural properties and critical current hysteresis of ceramic superconducting Bi sub 1 sub . sub 7 Pb sub 0 sub . sub 3 Sr sub 2 Ca sub 2 Cu sub 3 O sub y

CERN Document Server

Tepe, M; Abukay, D

2003-01-01

The effect of pelletization pressures on structural properties and critical current hysteresis of Bi sub 1 sub . sub 7 Pb sub 0 sub . sub 3 Sr sub 2 Ca sub 2 Cu sub 3 O sub y samples was investigated. The samples used in this study were prepared by classical solid-state reaction at the pressures from 100 up to 500 MPa. The obtained samples were characterized by resistance vs. temperature, (R-T), critical current density vs. applied magnetic field, (J sub c -H), material density vs. pressure, (rho-P), XRD, SEM, and EDAX. The results of this study showed that the quality of electrical and structural properties of Bi-2223 bulk superconductors strongly depends on the pelletization pressure. Pressing of bulk samples at 400 MPa produces textured grain alignment and associates microstructural modifications in order to enhance flux pinning and thus increases current carrying capacities. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

Estimated Critical Conditions for UO(Sub 2)F(Sub 2)-H(Sub 2)O Systems in Fully Water-Reflected Spherical Geometry

Energy Technology Data Exchange (ETDEWEB)

Jordan, W.C.

1992-01-01

The purpose of this report is to document reference calculations performed using the SCALE-4.0 code system to determine the critical parameters of UO{sub 2}F{sub 2}-H{sub 2}O spheres. The calculations are an extension of those documented in ORNL/CSD/TM-284. Specifically, the data for low-enriched UO{sub 2}F{sub 2}-H{sub 2}O spheres have been extended to highly enriched uranium. These calculations, together with those reported in ORNL/CSD/TM-284, provide a consistent set of critical parameters (k{sub {infinity}}, volume, mass, mass of water) for UO{sub 2}F{sub 2} and water over the full range of enrichment and moderation ratio.

Estimated critical conditions for UO{sub 2}F{sub 2}--H{sub 2}O systems in fully water-reflected spherical geometry

Energy Technology Data Exchange (ETDEWEB)

Jordan, W.C.; Turner, J.C.

1992-12-01

The purpose of this report is to document reference calculations performed using the SCALE-4.0 code system to determine the critical parameters of UO{sub 2}F{sub 2}-H{sub 2}O spheres. The calculations are an extension of those documented in ORNL/CSD/TM-284. Specifically, the data for low-enriched UO{sub 2}F{sub 2}-H{sub 2}O spheres have been extended to highly enriched uranium. These calculations, together with those reported in ORNL/CSD/TM-284, provide a consistent set of critical parameters (k{sub {infinity}}, volume, mass, mass of water) for UO{sub 2}F{sub 2} and water over the full range of enrichment and moderation ratio.

Hydrothermal synthesis of CdS/Bi{sub 2}MoO{sub 6} heterojunction photocatalysts with excellent visible-light-driven photocatalytic performance

Energy Technology Data Exchange (ETDEWEB)

Feng, Yi; Yan, Xu; Liu, Chunbo; Hong, Yuanzhi; Zhu, Lin; Zhou, Mingjun; Shi, Weidong, E-mail: swd1978@ujs.edu.cn

2015-10-30

Graphical abstract: - Highlights: • The novel CdS/Bi{sub 2}MoO{sub 6} heterojunction were synthesized for the first time via a two-step hydrothermal process. • The CdS/Bi{sub 2}MoO{sub 6} heterojunction exhibited an excellent visible-light-driven photocatalytic activity for RhB degradation. • The photocatalytic activity of this heterojunction also evaluated by TC, MB degradation. • The mechanism of this photocatalysis system was firstly proposed. - Abstract: A novel CdS/Bi{sub 2}MoO{sub 6} heterojunction photocatalysts were successfully prepared via two-step hydrothermal methods. The prepared samples were characterized by various physicochemical techniques, such as XRD, SEM, TEM, HRTEM, XPS, UV–vis and PL. The obtained samples exhibited highly photocatalytic activity toward the degradation of the different kinds of organic dyes and tetracycline in aqueous solution under visible light irradiation (λ > 420 nm). The optimum photocatalytic efficiency of CdS-2 sample for the degradation rhodamine B (RhB) was about 25.3 and 3.7 times higher than that of individual CdS and Bi{sub 2}MoO{sub 6}, respectively. In addition, the possible photocatalytic mechanism was analyzed by different active species trapping experiments. The results indicated that the h{sup +} and ·O{sub 2}{sup −} were the main active species for the photocatalytic degradation of RhB. Moreover, the prepared sample shows good stability and recyclability properties which are beneficial for its practical application.

Achieving simultaneous CO{sub 2} and H{sub 2}S conversion via a coupled solar-driven electrochemical approach on non-precious-metal catalysts

Energy Technology Data Exchange (ETDEWEB)

Ma, Weiguang; Yu, Wei; Zong, Xu; Li, Can [State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian National Laboratory for Clean Energy, The Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Dalian (China); Wang, Hong; Wang, Xiaomei; Xu, Zhiqiang [State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian National Laboratory for Clean Energy, The Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), Dalian (China); University of Chinese Academy of Sciences, Beijing (China)

2018-03-19

Carbon dioxide (CO{sub 2}) and hydrogen sulfide (H{sub 2}S) are generally concomitant with methane (CH{sub 4}) in natural gas and traditionally deemed useless or even harmful. Developing strategies that can simultaneously convert both CO{sub 2} and H{sub 2}S into value-added products is attractive; however it has not received enough attention. A solar-driven electrochemical process is demonstrated using graphene-encapsulated zinc oxide catalyst for CO{sub 2} reduction and graphene catalyst for H{sub 2}S oxidation mediated by EDTA-Fe{sup 2+}/EDTA-Fe{sup 3+} redox couples. The as-prepared solar-driven electrochemical system can realize the simultaneous conversion of CO{sub 2} and H{sub 2}S into carbon monoxide and elemental sulfur at near neutral conditions with high stability and selectivity. This conceptually provides an alternative avenue for the purification of natural gas with added economic and environmental benefits. (copyright 2018 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

Magneto-acoustic study near the quantum critical point of the frustrated quantum antiferromagnet Cs{sub 2}CuCl{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Cong, P. T., E-mail: t.pham@hzdr.de [Dresden High Magnetic Field Laboratory, Helmholtz-Zentrum Dresden-Rossendorf, D-01314 Dresden (Germany); Physics Institute, Goethe University Frankfurt, D-60438 Frankfurt am Main (Germany); Postulka, L.; Wolf, B.; Ritter, F.; Assmus, W.; Krellner, C.; Lang, M., E-mail: michael.lang@physik.uni-frankfurt.de [Physics Institute, Goethe University Frankfurt, D-60438 Frankfurt am Main (Germany); Well, N. van [Physics Institute, Goethe University Frankfurt, D-60438 Frankfurt am Main (Germany); Laboratory for Neutron Scattering and Imaging, Paul Scherrer Institute, CH-5232 Villigen (Switzerland)

2016-10-14

Magneto-acoustic investigations of the frustrated triangular-lattice antiferromagnet Cs{sub 2}CuCl{sub 4} were performed for the longitudinal modes c{sub 11} and c{sub 33} in magnetic fields along the a-axis. The temperature dependence of the sound velocity at zero field shows a mild softening at low temperature and displays a small kink-like anomaly at T{sub N}. Isothermal measurements at T < T{sub N} of the sound attenuation α reveal two closely spaced features of different characters on approaching the material's quantum-critical point (QCP) at B{sub s} ≈ 8.5 T for B || a. The peak at slightly lower fields remains sharp down to the lowest temperature and can be attributed to the ordering temperature T{sub N}(B). The second anomaly, which is rounded and which becomes reduced in size upon cooling, is assigned to the material's spin-liquid properties preceding the long-range antiferromagnetic ordering with decreasing temperature. These two features merge upon cooling suggesting a coincidence at the QCP. The elastic constant at lowest temperatures of our experiment at 32 mK can be well described by a Landau free energy model with a very small magnetoelastic coupling constant G/k{sub B} ≈ 2.8 K. The applicability of this classical model indicates the existence of a small gap in the magnetic excitation spectrum which drives the system away from quantum criticality.

Critical parameters in the sputter-deposition of NdBa{sub 2}Cu{sub 3}O{sub 7-{delta}} thin films

Energy Technology Data Exchange (ETDEWEB)

Hakuraku, Y.; Yokoyama, N.; Doi, T.; Inoue, T. [Faculty of Engineering, Kagoshima University, Koorimoto, Kagoshima 890, (Japan); Mori, Z.; Koba, S. [Yatsushiro National College of Technology, Yatsushiro 866 (Japan)

1999-08-01

A superconducting thin film of NdBa{sub 2}Cu{sub 3}O{sub 7-{delta}} (NBCO) was prepared on an MgO(100) substrate by dc magnetron sputtering. Superconducting properties as well as features such as resistivity at room temperature and surface morphology were improved by optimizing the composition of sputtering target and critical parameters such as substrate temperature and oxidation gas pressure. A highly c-axis oriented thin film with T{sub c} (zero resistance temperature) = 95.2 K was obtained reproducibly with NdBa{sub 2}Cu{sub 3.2}O{sub 7-{delta}} off-stoichiometric target sputtering. T{sub c} = 95.2 K was 8 K higher than that deposited by stoichiometric target sputtering. Critical current density was 1x10{sup 6} A cm{sup -2} at 77 K, and surface roughness was 35 nm. (author)

Critical current density of strained multilayer thin films of Nd sub 1. 83 Ce sub 0. 17 CuO sub x /YBa sub 2 Cu sub 3 O sub 7 minus. delta

Energy Technology Data Exchange (ETDEWEB)

Gross, R.; Gupta, A.; Olsson, E.; Segmueller, A.; Koren, G. (IBM T. J. Watson Research Center, P.O. Box 218, Yorktown Heights, New York 10598 (USA))

1990-07-09

The superconducting transport properties of strained multilayer thin films of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}/ Nd{sub 1.83}Ce{sub 0.17}CuO{sub {ital x}}, grown heteroepitaxially by laser ablation deposition, are reported. For individual layer thicknesses below a critical layer thickness of about 250 A, coherency strain removes the orthorhombic distortion in the YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} layers and makes them twin-free. Zero-field critical current densities as high as 1.1{times}10{sup 7} A/cm{sup 2} at 77 K have been measured for the YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} layers. Flux pinning energies at zero temperature and zero magnetic field in the range of 80--140 meV have been found.

Magnetic entropy change and critical exponents in double perovskite Y{sub 2}NiMnO{sub 6}

Energy Technology Data Exchange (ETDEWEB)

Sharma, G. [School of Physical Sciences, Jawaharlal Nehru University, New Delhi-110067 (India); Tripathi, T.S. [Inter-University Accelerator Centre, New Delhi-110067 (India); Saha, J. [School of Physical Sciences, Jawaharlal Nehru University, New Delhi-110067 (India); Patnaik, S., E-mail: spatnaik@mail.jnu.ac.in [School of Physical Sciences, Jawaharlal Nehru University, New Delhi-110067 (India)

2014-11-15

We report the magnetic entropy change (ΔS{sub M}) and the critical exponents in the double perovskite manganite Y{sub 2}NiMnO{sub 6} with a ferromagnetic to paramagnetic transition T{sub C}∼85K. For a magnetic field change ΔH=80kOe, a maximum magnetic entropy change ΔS{sub M}=−6.57J/kgK is recorded around T{sub C}. The critical exponents β=0.363±0.05 and γ=1.331±0.09 obtained from power law fitting to spontaneous magnetization M{sub S}(T) and the inverse initial susceptibility χ{sub 0}{sup −1}(T) satisfy well to values derived for a 3D-Heisenberg ferromagnet. The critical exponent δ=4.761±0.129 is determined from the isothermal magnetization at T{sub C}. The scaling exponents corresponding to second order phase transition are consistent with the exponents from Kouvel–Fisher analysis and satisfy Widom's scaling relation δ=1+(γ/β). Additionally, they also satisfy the single scaling equation M(H,ϵ)=ϵ{sup β}f±(H/ϵ{sup β+γ}) according to which the magnetization-field-temperature data around T{sub C} should collapse into two curves for temperatures below and above T{sub C}. - Highlights: • The magneto-caloric (MC) effect and the critical exponent analysis in Y{sub 2}NiMnO{sub 6} are studied. • Methods such as Kouvel–Fisher, Widom's and Mean-Field scaling are used. • The magnetic ground state in Y{sub 2}NiMnO{sub 6} is based on isotropic 3D Heisenberg model. • The large MC effect can be utilized towards magnetic refrigeration around 77 K. • The nearest neighbor interaction in Y{sub 2}NiMnO{sub 6} rules out ferroelectricity.

Critical behavior of the ferromagnetic-paramagnetic phase transition in Fe{sub 90−x}Ni{sub x}Zr{sub 10} alloy ribbons

Energy Technology Data Exchange (ETDEWEB)

Thanh, Tran Dang, E-mail: thanhxraylab@yahoo.com [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Institute of Materials Science, VAST, 18 Hoang Quoc Viet, Hanoi (Viet Nam); Huy Dan, Nguyen [Institute of Materials Science, VAST, 18 Hoang Quoc Viet, Hanoi (Viet Nam); Phan, The-Long; Yu, Seong-Cho, E-mail: scyu@chungbuk.ac.kr [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Kumarakuru, Haridas; Olivier, Ezra J.; Neethling, Johannes H. [Centre for HRTEM, Department of Physics, Nelson Mandela Metropolitan University, Port Elizabeth 6031 (South Africa)

2014-01-14

This work presents a detailed study on the critical behavior of the ferromagnetic-paramagnetic (FM-PM) phase transition in Fe{sub 90−x}Ni{sub x}Zr{sub 10} (x = 0 and 5) alloy ribbons. Basing on field dependences of magnetization (M-H), M{sup 2} versus H/M plots prove the alloys exhibiting a second-order magnetic phase transition. To investigate the nature of the FM-PM phase transition at T{sub C} = 245 and 306 K for x = 0 and 5, respectively, we performed a critical-exponent study. The values of critical components β, γ, and δ determined by using the modified Arrott plots, Kouvel-Fisher (KF), and critical isotherm analyses agree with each other. For x = 0, the critical parameters β = 0.365 ± 0.013 and γ = 1.615 ± 0.033 are obtained by modified Arrott plots while β = 0.368 ± 0.008 and γ = 1.612 ± 0.016 are obtained by the KF method. These values are close to those expected for the 3D-Heisenberg model, revealing short-range FM interactions in Fe{sub 90}Zr{sub 10}. Meanwhile, for x = 5, the values of the critical parameters β = 0.423 ± 0.008 and γ = 1.325 ± 0.036 are obtained by modified Arrott plots, and β = 0.425 ± 0.006 and γ = 1.323 ± 0.012 are obtained by the KF method. The falling of the β value in between the values of the mean-field theory (β = 0.5) and the 3D-Heisenberg model (β = 0.365) indicates an existence of FM short-range order and magnetic inhomogeneity in Fe{sub 85}Ni{sub 5}Zr{sub 10}. With a partial replacement of Ni for Fe in Fe{sub 90−x}Ni{sub x}Zr{sub 10}, the value of the critical exponent β trends to shift towards that of the mean-field theory. Such the result proves the presence of Ni favors establishing FM long-range order. The nature of this phenomenon is carefully discussed.

Daylight-driven photocatalytic degradation of ionic dyes with negatively surface-charged In{sub 2}S{sub 3} nanoflowers: dye charge-dependent roles of reactive species

Energy Technology Data Exchange (ETDEWEB)

Ge, Suxiang [Xuchang University, Key Laboratory of Micro-Nano Materials for Energy Storage and Conversion of Henan Province, Institute of Surface Micro and Nano Materials, and School of Chemistry and Chemical Engineering (China); Cai, Lejuan, E-mail: 494169965@qq.com [Central China Normal University, Key Laboratory of Pesticide and Chemical Biology of Ministry of Education, College of Chemistry (China); Li, Dapeng, E-mail: lidapengabc@126.com; Fa, Wenjun; Zhang, Yange; Zheng, Zhi [Xuchang University, Key Laboratory of Micro-Nano Materials for Energy Storage and Conversion of Henan Province, Institute of Surface Micro and Nano Materials, and School of Chemistry and Chemical Engineering (China)

2015-12-15

Even though dye degradation is a successful application of semiconductor photocatalysis, the roles of reactive species in dye degradation have not received adequate attention. In this study, we systematically investigated the degradation of two cationic dyes (rhodamine B and methylene blue) and two anionic dyes (methyl orange and orange G) over negatively surface-charged In{sub 2}S{sub 3} nanoflowers synthesized at 80 °C under indoor daylight lamp irradiation. It is notable to find In{sub 2}S{sub 3} nanoflowers were more stable in anionic dyes degradation compared to that in cationic dyes removal. The active species trapping experiments indicated photogenerated electrons were mainly responsible for cationic dyes degradation, but holes were more important in anionic dyes degradation. A surface-charge-dependent role of reactive species in ionic dye degradation was proposed for revealing such interesting phenomenon. This study would provide a new insight for preparing highly efficient daylight-driven photocatalyst for ionic dyes degradation.

Lightwave-driven quasiparticle collisions on a sub-cycle timescale

Science.gov (United States)

Langer, F.; Hohenleutner, M.; Schmid, C.; Poellmann, C.; Nagler, P.; Korn, T.; Schüller, C.; Sherwin, M. S.; Huttner, U.; Steiner, J. T.; Koch, S. W.; Kira, M.; Huber, R.

2016-01-01

Ever since Ernest Rutherford first scattered α-particles from gold foils1, collision experiments have revealed unique insights into atoms, nuclei, and elementary particles2. In solids, many-body correlations also lead to characteristic resonances3, called quasiparticles, such as excitons, dropletons4, polarons, or Cooper pairs. Their structure and dynamics define spectacular macroscopic phenomena, ranging from Mott insulating states via spontaneous spin and charge order to high-temperature superconductivity5. Fundamental research would immensely benefit from quasiparticle colliders, but the notoriously short lifetimes of quasiparticles6 have challenged practical solutions. Here we exploit lightwave-driven charge transport7–24, the backbone of attosecond science9–13, to explore ultrafast quasiparticle collisions directly in the time domain: A femtosecond optical pulse creates excitonic electron–hole pairs in the layered dichalcogenide tungsten diselenide while a strong terahertz field accelerates and collides the electrons with the holes. The underlying wave packet dynamics, including collision, pair annihilation, quantum interference and dephasing, are detected as light emission in high-order spectral sidebands17–19 of the optical excitation. A full quantum theory explains our observations microscopically. This approach opens the door to collision experiments with a broad variety of complex quasiparticles and suggests a promising new way of sub-femtosecond pulse generation. PMID:27172045

Physics study of D-D/D-T neutron driven experimental subcritical assembly

International Nuclear Information System (INIS)

Sinha, Amar

2015-01-01

An experimental program to design and study external source driven subcritical assembly has been initiated at BARC. This program is aimed at understanding neutronic characteristics of accelerator driven system at low power level. In this series, a zero-power, sub-critical assembly driven by a D-D/D-T neutron generator has been developed. This system is modular in design and it is first in the series of subcritical assemblies being designed. The subcritical core consists of natural uranium fuel with high density polyethylene as moderator and beryllium oxide as reflector. The subcritical core is coupled to Purnima Neutron Generator. Preliminary experiments have been carried out for spatial flux measurement and reactivity estimation using pulsed neutron source (PNS) techniques. Further experiments are being planned to measure the reactivity and other kinetic parameters using noise methods. This facility would also be used for carrying out studies on effect of source importance and measurement of source multiplication factor k s and external neutron source efficiency φ* in great details. Some experiments with D-D and D-T neutrons have been presented. (author)

Effect of anisotropic strain on the quantum critical phase of Sr{sub 3}Ru{sub 2}O{sub 7}

Energy Technology Data Exchange (ETDEWEB)

Brodsky, Daniel; Barber, Mark; Mackenzie, Andrew [MPI-Chemische Physik fester Stoffe, Dresden (Germany); Scottish Universities Physics Alliance (SUPA), School of Physics and Astronomy, University of St Andrews, St Andrews (United Kingdom); Hicks, Clifford [MPI-Chemische Physik fester Stoffe, Dresden (Germany); Perry, Robin [SUPA, School of Physics, University of Edinburgh, Edinburgh (United Kingdom)

2015-07-01

We have developed a novel piezoelectric-based device for applying both compressive and tensile strains to single crystals. One particularly appealing target for such studies is Sr{sub 3}Ru{sub 2}O{sub 7}. Sr{sub 3}Ru{sub 2}O{sub 7} has a novel quantum critical phase around a metamagnetic transition at 8 T, which shows very strong transport anisotropy in the presence of weak symmetry-breaking fields. We discuss the response of this phase to applied anisotropic lattice strain.

Tales to Transit : Sub-Saharan African Migrants’ Experiences in Istanbul

OpenAIRE

Suter, Brigitte

2012-01-01

This dissertation presents the transit experiences of migrants from Sub-Saharan African countries in the Turkish metropolis of Istanbul. Although the narratives of the individuals met in the course of fieldwork in Istanbul are the primary focus, the thesis also outlines the larger macro-structural conditions faced. The overarching goal of this thesis is thus, through the experiences of the migrants themselves, to critically approach and discuss the concept of transit with the aid of the theor...

Spin-driven pyroelectricity in Ni{sub 3}TeO{sub 6} without ferroelectric signatures of the transition at Neel temperature

Energy Technology Data Exchange (ETDEWEB)

Zhao, L.; Komarek, A.C. [Max-Planck-Institute for Chemical Physics of Solids, Dresden (Germany); Du, C.H. [Department of Physics, Tamkang University, Tamsui, Taiwan (China)

2017-07-15

Here we report on dielectric studies on Ni{sub 3}TeO{sub 6}. We confirm the spin-driven pyroelectric transition at the Neel temperature (T{sub N}) of ∝52.5 K. The measurement of single crystalline and polycrystalline samples excludes a ferroelectric nature of the transition at T{sub N} in this compound. The excellent pyroelectric properties without any intrinsic ferroelectric hysteresis make Ni{sub 3}TeO{sub 6} appropriate for applications in future devices. Pyroelectric measurements on our Ni{sub 3}TeO{sub 6} single crystals. The polarization that appears on cooling through T{sub N} can not be inverted by opposite poling fields (applied when cooling from above T{sub N} to base temperature). (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Criticality experiments with low enriched UO2 fuel rods in water containing dissolved gadolinium

International Nuclear Information System (INIS)

Bierman, S.R.; Murphy, E.S.; Clayton, E.D.; Keay, R.T.

1984-02-01

The results obtained in a criticality experiments program performed for British Nuclear Fuels, Ltd. (BNFL) under contract with the United States Department of Energy (USDOE) are presented in this report along with a complete description of the experiments. The experiments involved low enriched UO 2 and PuO 2 -UO 2 fuel rods in water containing dissolved gadolinium, and are in direct support of BNFL plans to use soluble compounds of the neutron poison gadolinium as a primary criticality safeguard in the reprocessing of low enriched nuclear fuels. The experiments were designed primarily to provide data for validating a calculation method being developed for BNFL design and safety assessments, and to obtain data for the use of gadolinium as a neutron poison in nuclear chemical plant operations - particularly fuel dissolution. The experiments program covers a wide range of neutron moderation (near optimum to very under-moderated) and a wide range of gadolinium concentration (zero to about 2.5 g Gd/l). The measurements provide critical and subcritical k/sub eff/ data (1 greater than or equal to k/sub eff/ greater than or equal to 0.87) on fuel-water assemblies of UO 2 rods at two enrichments (2.35 wt % and 4.31 wt % 235 U) and on mixed fuel-water assemblies of UO 2 and PuO 2 -UO 2 rods containing 4.31 wt % 235 U and 2 wt % PuO 2 in natural UO 2 respectively. Critical size of the lattices was determined with water containing no gadolinium and with water containing dissolved gadolinium nitrate. Pulsed neutron source measurements were performed to determine subcritical k/sub eff/ values as additional amounts of gadolinium were successively dissolved in the water of each critical assembly. Fission rate measurements in 235 U using solid state track recorders were made in each of the three unpoisoned critical assemblies, and in the near-optimum moderated and the close-packed poisoned assemblies of this fuel

Synthesis and visible-light-driven photocatalytic activity of p–n heterojunction Ag{sub 2}O/NaTaO{sub 3} nanocubes

Energy Technology Data Exchange (ETDEWEB)

Yang, Songbo [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Xu, Dongbo [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); School of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013 (China); Chen, Biyi; Luo, Bifu [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Yan, Xu [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); School of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013 (China); Xiao, Lisong, E-mail: xiaolisong123@sina.com [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Shi, Weidong, E-mail: swd1978@ujs.edu.cn [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China)

2016-10-15

Highlights: • We firstly report a facile way to prepare the visible-light-driven Ag{sub 2}O/NaTaO{sub 3}p–n heterojunction by chemical precipitation method. • The Ag{sub 2}O/NaTaO{sub 3} heterojunction shows the highest photocatalytic activity than the pure NaTaO{sub 3} and Ag{sub 2}O nanoparticles under visible light. • The enhancement of the heterojunction photocatalytic activity was discussed and the photocatalytic mechanism was tested in our paper. • In summary, we think that the Ag{sub 2}O/NaTaO{sub 3} heterojunction with the strong visible light absorption and efficient photocatalytic activity have been extended application in photocatalysis for organic dyes pollutants degradation and purification of water. - Abstract: The constructing of p–n heterojunction photocatalytic system has received much attention in environmental purification and hydrogen generation from water. In this study, an efficient visible-light-driven p–n heterojunction Ag{sub 2}O/NaTaO{sub 3} was successfully prepared by chemical precipitation method at room temperature. It showed an enhanced photocatalytic activity for the degradation of rhodamine B (RhB) under visible-light irradiation, much higher than those of either individual Ag{sub 2}O or NaTaO{sub 3}. The reactive species scavenger results indicated the superoxide anion radicals (·O{sup 2−}) played key roles in RhB decoloration. From the experimental results and the relative band gap position of these semiconductors, a detailed possible photocatalytic mechanism of the Ag{sub 2}O/NaTaO{sub 3} heterojunction under visible light was proposed. The enhancement of the photocatalytic activity was attributed to the interfacial electronic interaction between NaTaO{sub 3} and Ag{sub 2}O and the high migration efficiency of photogenerated carriers.

Critical Path Driven Cosynthesis for Heterogeneous Target Architectures

DEFF Research Database (Denmark)

Bjørn-Jørgensen, Peter; Madsen, Jan

1997-01-01

This paper presents a critical path driven algorithm to produce a static schedule of a single-rate system onto a heterogeneous target architecture. Our algorithm is a list based scheduling algorithm which concurrently assigns tasks to processors and allocates nets to interprocessor communication........ Experimental results show that our algorithm is able to find good results, as compared to other methods, in small amount of CPU time....

Stimulated scattering in laser driven fusion and high energy density physics experiments

Energy Technology Data Exchange (ETDEWEB)

Yin, L., E-mail: lyin@lanl.gov; Albright, B. J.; Rose, H. A.; Montgomery, D. S.; Kline, J. L.; Finnegan, S. M.; Bergen, B.; Bowers, K. J. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Kirkwood, R. K.; Milovich, J. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

2014-09-15

In laser driven fusion and high energy density physics experiments, one often encounters a kλ{sub D} range of 0.15 < kλ{sub D} < 0.5, where stimulated Raman scattering (SRS) is active (k is the initial electron plasma wave number and λ{sub D} is the Debye length). Using particle-in-cell simulations, the SRS reflectivity is found to scale as ∼ (kλ{sub D}){sup −4} for kλ{sub D} ≳ 0.3 where electron trapping effects dominate SRS saturation; the reflectivity scaling deviates from the above for kλ{sub D} < 0.3 when Langmuir decay instability (LDI) is present. The SRS risk is shown to be highest for kλ{sub D} between 0.2 and 0.3. SRS re-scattering processes are found to be unimportant under conditions relevant to ignition experiments at the National Ignition Facility (NIF). Large-scale simulations of the hohlraum plasma show that the SRS wavelength spectrum peaks below 600 nm, consistent with most measured NIF spectra, and that nonlinear trapping in the presence of plasma gradients determines the SRS spectral peak. Collisional effects on SRS, stimulated Brillouin scattering (SBS), LDI, and re-scatter, together with three dimensional effects, are examined. Effects of collisions are found to include de-trapping as well as cross-speckle electron temperature variation from collisional heating, the latter of which reduces gain, introduces a positive frequency shift that counters the trapping-induced negative frequency shift, and affects SRS and SBS saturation. Bowing and breakup of ion-acoustic wavefronts saturate SBS and cause a dramatic, sharp decrease in SBS reflectivity. Mitigation of SRS and SBS in the strongly nonlinear trapping regime is discussed.

Kinetic analysis of sub-prompt-critical reactor assemblies

International Nuclear Information System (INIS)

Das, S.

1992-01-01

Neutronic analysis of safety-related kinetics problems in experimental neutron multiplying assemblies has been carried out using a sub-prompt-critical reactor model. The model is based on the concept of a sub-prompt-critical nuclear reactor and the concept of instantaneous neutron multiplication in a reactor system. Computations of reactor power, period and reactivity using the model show excellent agreement with results obtained from exact kinetics method. Analytic expressions for the energy released in a controlled nuclear power excursion are derived. Application of the model to a Pulsed Fast Reactor gives its sensitivity between 4 and 5. (author). 6 refs., 4 figs., 1 tab

Criticality experiments with annular cylinders containing plutonium solutions; Experiences de criticite sur des cylindres annulaires contenant des solutions de plutonium

Energy Technology Data Exchange (ETDEWEB)

Molbert, M; Sauve, A; Houelle, M; Deilgat, E [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1964-07-01

The criticality station of Dijon involves three cells, shielded by concrete walls of 1.46 meter thickness. Those cells are designed to contain the criticality experiment apparatus. The engineering building is also involving: one chemical laboratory where plutonium solutions are prepared, one analysis laboratory, several activated solutions storages, several control rooms, One cell contains the B system, which is designed to study: annular cylindrical geometries, slab of 10 cm thickness, interaction between annular cylinders. This report includes the first results given by experiments on annular cylinders defined by their own geometry (outer and inner diameter of ring containing plutonium solutions). Those results have been plotted in curves, for several concentrations and for different reflection conditions (outer or inner light water reflector, cadmium screen), H{sub c} and M{sub c} = f (c) (where H{sub c} is the critical height of solution, M{sub c} is the critical mass, c is the plutonium concentration: 42,3 g/lsub c} and M{sub c} versus the distance between the two solutions. - an insulated annular cylinder 500 x 200: incomplete results are published the experiments on this cylinder being unfinished to the date of this present report publication. On this miscellaneous results, we have following informations know: - Screen effect of light water in central hole. Strengthened effect by cadmium foil on the inside wall. - Normalized interaction curves ( {alpha}*H{sub c}/H{sub c{infinity}} ) versus the distance between the two vessels, where H{sub c{infinity}} critical height of an insulated cylinder, shows that: 1) In light water, two cylinders set aside from 15 cm, can be considers like separated. 2) For some configurations, {alpha} vary

Direct evidence for the first-order phase transition at the lower critical temperature in Er/sub 1-x/Ho/sub x/Rh4B4

International Nuclear Information System (INIS)

Lachal, B.; Ishikawa, M.; Junod, A.; Muller, J.

1982-01-01

Using a heat-pulse and a relaxation technique, we have performed an extensive calorimetric investigation on the reetrant superconductors Er/sub 1-x/Ho/sub x/Rh 4 B 4 (x = 0.4 and 0.6) around their lower critical temperature. These experiments revealed a supercooling effect and thermal hystersis, thus establishing the first-order nature of the transition. Based on the measurement of the latent heat, our thermodynamic analysis suggests that the onset of ferromagnetism is lowered by only 55 mK due to the competing superconducting phase. Results of magnetization and ac susceptibility experiments on these compounds are also included

Unusually high critical current of P-doped BaFe{sub 2}As{sub 2} single crystalline thin film

Energy Technology Data Exchange (ETDEWEB)

Kurth, Fritz; Engelmann, Jan; Schultz, Ludwig [IMW, IFW Dresden, Dresden (Germany); TU Dresden, Dresden (Germany); Tarantini, Chiara; Jaroszynski, Jan [ASC, NHMFL, Florida (United States); Grinenko, Vadim; Reich, Elke; Huehne, Ruben [IMW, IFW Dresden, Dresden (Germany); Haenisch, Jens [IMW, IFW Dresden, Dresden (Germany); ITEP, KIT, Karlsruhe (Germany); Mori, Yasohiro; Sakagami, Akihiro; Kawaguchi, Takahiko; Ikuta, Hiroshi [Department of Crystalline Materials Science, Nagoya University, Nagoya (Japan); Holzapfel, Bernhard [ITEP, KIT, Karlsruhe (Germany); Iida, Kazumasa [IMW, IFW Dresden, Dresden (Germany); Department of Crystalline Materials Science, Nagoya University, Nagoya (Japan)

2015-07-01

Microstructurally clean, isovalently P-doped BaFe{sub 2}As{sub 2} single crystalline thin films have been prepared by molecular beam epitaxy. These films show a superconducting transition temperature (T{sub c}) of over 30 K and high transport self-field critical current densities (J{sub c}) of over 6 MA/cm{sup 2} at 4.2 K, which are among the highest for Fe based superconductors. In-field J{sub c} exceeds 0.1 MA/cm{sup 2} at μ{sub 0}H = 35 T for H parallel ab and μ{sub 0}H = 18 T for H parallel c, respectively, in spite of moderate upper critical fields compared to other FeSCs with similar T{sub c}. This unusually high J{sub c} makes P-doped Ba-122 very favorable for high-field magnet applications.

Research project on accelerator-driven subcritical system using FFAG accelerator and Kyoto University critical assembly

International Nuclear Information System (INIS)

Mishima, Kaichiro; Unesaki, Hironobu; Misawa, Tsuyoshi; Tanigaki, Minoru; Mori, Yoshiharu; Shiroya, Seiji; Inoue, Makoto; Ishi, Y.; Fukumoto, Shintaro

2005-01-01

The KART (Kumatori Accelerator-driven Reactor Test facility) project started in Research Reactor Institute, Kyoto University in fiscal year 2002 with the grant by the Japanese Ministry of Education, Culture, Sports, Science and Technology. The purpose of this research project is to demonstrate the basis feasibility of accelerator driven system (ADS), studying the effect of incident neutron energy on the effective multiplication factor in a subcritical nuclear fuel system. For this purpose, a variable-energy FFAG (Fixed Field Alternating Gradient) accelerator complex is being constructed to be coupled with the Kyoto University Critical Assembly (KUCA). The FFAG proton accelerator complex consists of ion-beta, booster and main rings. This system aims to attain 1 μA proton beam with energy range from 20 to 150 MeV with a repetition rate of 120 Hz. The first beam from the FFAG complex is expected to be available by the end of FY 2005, and the experiment on ADS with KUCA and the FFAG complex (FFAG-KUCA experiment) will start in FY 2006. Before the FFAG-KUCA experiment starts, preliminary experiments with 14 MeV neutrons are currently being performed using a Cockcroft-Walton type accelerator coupled with the KUCA. Experimental data are analyzed using continuous energy Monte-Carlo codes MVP, MCNP and MNCP-X. (author)

High critical currents in heavily doped (Gd,Y)Ba{sub 2}Cu{sub 3}O{sub x} superconductor tapes

Energy Technology Data Exchange (ETDEWEB)

Selvamanickam, V., E-mail: selva@uh.edu; Gharahcheshmeh, M. Heydari; Xu, A.; Galstyan, E.; Delgado, L. [Department of Mechanical Engineering and Texas Center for Superconductivity, University of Houston, 4800 Calhoun Rd., Houston, Texas 77204-4006 (United States); Cantoni, C. [Oak Ridge National Laboratory, Oak Ridge, Tennessee 37381 (United States)

2015-01-19

REBa{sub 2}Cu{sub 3}O{sub x} ((REBCO), RE = rare earth) superconductor tapes with moderate levels of dopants have been optimized for high critical current density in low magnetic fields at 77 K, but they do not exhibit exemplary performance in conditions of interest for practical applications, i.e., temperatures less than 50 K and fields of 2–30 T. Heavy doping of REBCO tapes has been avoided by researchers thus far due to deterioration in properties. Here, we report achievement of critical current densities (J{sub c}) above 20 MA/cm{sup 2} at 30 K, 3 T in heavily doped (25 mol. % Zr-added) (Gd,Y)Ba{sub 2}Cu{sub 3}O{sub x} superconductor tapes, which is more than three times higher than the J{sub c} typically obtained in moderately doped tapes. Pinning force levels above 1000 GN/m{sup 3} have also been attained at 20 K. A composition map of lift factor in J{sub c} (ratio of J{sub c} at 30 K, 3 T to the J{sub c} at 77 K, 0 T) has been developed which reveals the optimum film composition to obtain lift factors above six, which is thrice the typical value. A highly c-axis aligned BaZrO{sub 3} (BZO) nanocolumn defect density of nearly 7 × 10{sup 11 }cm{sup −2} as well as 2–3 nm sized particles rich in Cu and Zr have been found in the high J{sub c} films.

Modelling of an experiment for the study of neutron spallation source at JINR

International Nuclear Information System (INIS)

Kumawat, Harphool; Goyal, Uttam; Kumar, V.; Barashenkov, V.S.

2002-01-01

Intense neutron spallation source (INSS) is a necessary requirement of accelerator driven sub-critical systems. INSS are proposed to be generated using the high current proton beams. Some studies are conducted for the neutron flux, transmutation rates and energy gains and a larger number of related experiments are being planned

Critical parameters near the ferromagnetic-paramagnetic phase transition in La{sub 0.7}A{sub 0.3}(Mn{sub 1-x}b{sub x})O{sub 3} (A=Sr; B=Ti and Al; x=0.0 and 0.05) compounds

Energy Technology Data Exchange (ETDEWEB)

Khiem, N.V. [Hongduc University, 307 Lelai Street, Thanhhoa City (Viet Nam)], E-mail: nvkhiem2002@yahoo.com; Phong, P.T. [Institute of Materials Science, Vietnamese Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay District, Hanoi (Viet Nam); Bau, L.V. [Hongduc University, 307 Lelai Street, Thanhhoa City (Viet Nam); Nam, D.N.H.; Hong, L.V.; Phuc, N.X. [Institute of Materials Science, Vietnamese Academy of Science and Technology, 18 Hoang Quoc Viet Road, Cau Giay District, Hanoi (Viet Nam)

2009-07-15

The critical parameters provide important information concerning the interaction mechanisms near the paramagnetic-to-ferromagnetic transition. In this paper, we present a thorough study for the critical behavior of La{sub 0.7}A{sub 0.3}(Mn{sub 1-x}B{sub x})O{sub 3} (A=Sr; B=Ti and Al; x=0.0 and 0.05) polycrystalline samples near ferromagnetic-paramagnetic phase transition temperature by analyzing isothermal magnetization data. We have analyzed our dc-magnetization data near the transition temperature with the help of the modified Arrot plot, Kouvel-Fisher method. We have determined the critical temperature T{sub C} and the critical parameters {beta}, {gamma} and {delta}. With the values of T{sub C}, {beta} and {gamma}, we plot Mx(1-T/T{sub C}){sup -{beta}} vs. Hx(1-T/T{sub C}){sup -{gamma}}. All the data collapse on one of the two curves. This suggests that the data below and above T{sub C} obey scaling, following a single equation of state. Critical parameters for x=0 and x{sub Ti}=0.05 samples are between those predicted for a 3D-Heisenberg model and mean-field theory and for x{sub Al}=0.05 samples the values obtained for the critical parameters are close to those predicted by the mean-field theory.

Characteristic signatures of quantum criticality driven by geometrical frustration.

Science.gov (United States)

Tokiwa, Yoshifumi; Stingl, Christian; Kim, Moo-Sung; Takabatake, Toshiro; Gegenwart, Philipp

2015-04-01

Geometrical frustration describes situations where interactions are incompatible with the lattice geometry and stabilizes exotic phases such as spin liquids. Whether geometrical frustration of magnetic interactions in metals can induce unconventional quantum critical points is an active area of research. We focus on the hexagonal heavy fermion metal CeRhSn, where the Kondo ions are located on distorted kagome planes stacked along the c axis. Low-temperature specific heat, thermal expansion, and magnetic Grüneisen parameter measurements prove a zero-field quantum critical point. The linear thermal expansion, which measures the initial uniaxial pressure derivative of the entropy, displays a striking anisotropy. Critical and noncritical behaviors along and perpendicular to the kagome planes, respectively, prove that quantum criticality is driven be geometrical frustration. We also discovered a spin flop-type metamagnetic crossover. This excludes an itinerant scenario and suggests that quantum criticality is related to local moments in a spin liquid-like state.

Perturbative Field-Theoretical Renormalization Group Approach to Driven-Dissipative Bose-Einstein Criticality

Directory of Open Access Journals (Sweden)

Uwe C. Täuber

2014-04-01

Full Text Available The universal critical behavior of the driven-dissipative nonequilibrium Bose-Einstein condensation transition is investigated employing the field-theoretical renormalization group method. Such criticality may be realized in broad ranges of driven open systems on the interface of quantum optics and many-body physics, from exciton-polariton condensates to cold atomic gases. The starting point is a noisy and dissipative Gross-Pitaevski equation corresponding to a complex-valued Landau-Ginzburg functional, which captures the near critical nonequilibrium dynamics, and generalizes model A for classical relaxational dynamics with nonconserved order parameter. We confirm and further develop the physical picture previously established by means of a functional renormalization group study of this system. Complementing this earlier numerical analysis, we analytically compute the static and dynamical critical exponents at the condensation transition to lowest nontrivial order in the dimensional ε expansion about the upper critical dimension d_{c}=4 and establish the emergence of a novel universal scaling exponent associated with the nonequilibrium drive. We also discuss the corresponding situation for a conserved order parameter field, i.e., (subdiffusive model B with complex coefficients.

Alecto - results obtained with homogeneous critical experiments on plutonium 239, uranium 235 and uranium 233; Alecto - resultats des experiences critiques homogenes realisees sur le plutonium 239, l'uranium 235 et l'uranium 233

Energy Technology Data Exchange (ETDEWEB)

Bruna, J G; Brunet, J P; Caizegues, R; Clouet d' Orval, Ch; Kremser, J; Tellier, H; Verriere, Ph [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1965-07-01

In this report are given the results of the homogeneous critical experiments ALECTO, made on plutonium 239, uranium 235 and uranium 233. After a brief description of the equipment, the critical masses for cylinders of diameters varying from 25 to 42 cm, are given and compared with other values (foreign results, criticality guide). With respect to the specific conditions of neutron reflection in the ALECTO experiments the minimal values of critical masses are: Pu239 M{sub c} = 910 {+-} 10 g, U235 M{sub c} = 1180 {+-} 12 g and U233 M{sub c} = 960 {+-} 10 g. Experiments relating to cross sections and constants to be used on these materials are presented. Lastly, kinetic experiments allow to compare pulsed neutron methods to fluctuation methods. [French] On presente dans ce rapport les resultats des experiences critiques homogenes ALECTO, effectuees sur le plutonium 239, l'uranium 235 et l'uranium 233. Apres avoir rappele la description des installations, on donne les masses critiques pour des cylindres de diametres variant entre 25 et 42 cm, qui sont comparees avec d'autres chiffres (resultats etrangers, guide de criticite). Dans les gammes des diametres etudies pour des cuves a fond plat reflechies lateralement, la valeur minimale des masses critiques est la suivante: Pu239 M{sub c} = 910 {+-} 10 g, U235 M{sub c} = 1180 {+-} 12 g et U233 M{sub c} 960 {+-} 10 g. Des experiences portant sur les sections efficaces et les constantes a utiliser sur ces milieux sont ensuite presentees. Enfin des experiences de cinetique permettent une comparaison entre la methode des neutrons pulses et la methode des fluctuations. (auteur)

Design of an accelerator-driven system for the destruction of nuclear waste

International Nuclear Information System (INIS)

Kadi, Y.; Revol, J.P.

2003-01-01

Progress in particle accelerator technology makes it possible to use a proton accelerator to produce energy and to destroy nuclear waste efficiently. The Energy Amplifier (EA) proposed by Carlo Rubbia and his group is a sub-critical fast neutron system driven by a proton accelerator. It is particularly attractive for destroying, through fission, transuranic elements produced by present nuclear reactors. The EA could also transform efficiently and at minimal cost long-lived fission fragments using the concept of Adiabatic Resonance Crossing (ARC) recently tested at CERN with the TARC experiment. (author)

Critical and Exponential Experiments on 19-Rod Clusters (R3 Fuel) in Heavy Water

Energy Technology Data Exchange (ETDEWEB)

Persson, R; Wikdahl, C E; Zadworski, Z

1962-03-15

Buckling measurements on clusters of 19 UO{sub 2} rods in heavy water have been performed in an exponential assembly and by means of substitution measurements in a critical facility. The material buckling was determined as a function of lattice pitch (range of V{sub mod} /V{sub fuel}: 7-22), internal spacing, void, and temperature (20 < T < 90 deg C). The change of diffusion coefficients (about 6-8 per cent) caused by voids was studied with single test fuel assemblies. The progressive substitution measurements have been analysed by means of a modified one-group perturbation theory in combination with an unconventional cell definition. The buckling differences between test and reference lattices are of the order of -1.0 to -3.5/m{sup 2}, The results of the exponential and the critical experiments are compared with similar measurements on the same kind of fuel at the Savannah River Laboratory. This comparison shows that the results of the various experiments agree quite well, whereas theoretical predictions fail in the extreme ranges.

Intermittency and transition to chaos in the cubical lid-driven cavity flow

Energy Technology Data Exchange (ETDEWEB)

Loiseau, J-Ch [Department of Mechanics, Royal Institute of Technology (KTH), SE-100 44 Stockholm (Sweden); Robinet, J-Ch [Laboratoire DynFluid, Arts et Métiers ParisTech, F-75013 Paris (France); Leriche, E, E-mail: loiseau@mech.kth.se [Laboratoire de Mécanique de Lille, Université Lille 1, F-59655 Villeneuve d’Ascq (France)

2016-12-15

Transition from steady state to intermittent chaos in the cubical lid-driven cavity flow is investigated numerically. Fully three-dimensional stability analyses have revealed that the flow experiences an Andronov–Poincaré–Hopf bifurcation at a critical Reynolds number Re {sub c} = 1914. As for the 2D-periodic lid-driven cavity flows, the unstable mode originates from a centrifugal instability of the primary vortex core. A Reynolds–Orr analysis reveals that the unstable perturbation relies on a combination of the lift-up and anti lift-up mechanisms to extract its energy from the base flow. Once linearly unstable, direct numerical simulations show that the flow is driven toward a primary limit cycle before eventually exhibiting intermittent chaotic dynamics. Though only one eigenpair of the linearized Navier–Stokes operator is unstable, the dynamics during the intermittencies are surprisingly well characterized by one of the stable eigenpairs. (paper)

Accelerator driven radiation clean nuclear power system conceptual research symposium

International Nuclear Information System (INIS)

Zhao Zhixiang

2000-06-01

The R and D of ADS (Accelerators Driven Subcritical System) in China introduced. 31 theses are presented. It includes the basic principle of ADS, accelerators, sub-critical reactors, neutron physics, nuclear data, partitioning and transmutation

Critical slowing down in driven-dissipative Bose-Hubbard lattices

Science.gov (United States)

Vicentini, Filippo; Minganti, Fabrizio; Rota, Riccardo; Orso, Giuliano; Ciuti, Cristiano

2018-01-01

We explore theoretically the dynamical properties of a first-order dissipative phase transition in coherently driven Bose-Hubbard systems, describing, e.g., lattices of coupled nonlinear optical cavities. Via stochastic trajectory calculations based on the truncated Wigner approximation, we investigate the dynamical behavior as a function of system size for one-dimensional (1D) and 2D square lattices in the regime where mean-field theory predicts nonlinear bistability. We show that a critical slowing down emerges for increasing number of sites in 2D square lattices, while it is absent in 1D arrays. We characterize the peculiar properties of the collective phases in the critical region.

A formulation for the critical temperature T/sub c/ of Ll2-type superconductors

International Nuclear Information System (INIS)

Wang Rong-Yao; Zhang Xiao

1985-01-01

From the examination of Ll 2 type superconductors, the superconducting critical temperature T/sub b/ of Ll 2 -type superconductors is obtained by: T/sub c/ = 15.9T/sub B/V(B)G/sub A//(√M/sub m/) V(Ll 2 )/sub m/ G/sub B/ where T/sub B/ is the superconducting critical temperature of pure B, V(B) the atomic volume in pure B, V(Ll 2 )/sub m/ the average atomic volume in the Ll 2 type compound, M/sub m/ the average atomic weight of the compound, and G/sub A/, G/sub B/ are the Gordy electronegative values. (author)

Effect of doping with magnetic 3D-elements on the thermal fluctuations and critical parameters of CaLaBaCu{sub 3-x}(Ni,Co){sub x}O{sub 7-{delta}} superconductors

Energy Technology Data Exchange (ETDEWEB)

Rojas Sarmiento, M.P.; Landinez Tellez, D.A. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, AA 14490, Bogota DC (Colombia); Roa-Rojas, J. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, AA 14490, Bogota DC (Colombia)], E-mail: jroar@unal.edu.co

2008-07-15

Systematic measurements on conductivity fluctuation in the CaLaBaCu{sub 3-x}(Ni,Co){sub x}O{sub 7-{delta}} system are reported. Samples with x=0, 0.03, 0.06, 0.09, 0.12, 0.15 and 0.18 were prepared by the standard solid-state reaction recipe. Results of resistivity measurements reveal a linear-like decreasing of the critical temperature T{sub c} with progressive substitution of magnetic elements Ni and Co into the Cu crystallographic sites. From the fluctuation analysis, above and close to T{sub c}, we found the occurrence of three- and two-dimensional Gaussian fluctuation regimes. Closer to T{sub c}, a genuinely critical regime is observed. On the Ginzburg-Landau formalism, from the reduced temperature of the three-dimensional Gaussian region and the mean field critical temperature, we have experimentally obtained the Ginzburg number for the CaLaBaCu{sub 3-x}(Ni,Co){sub x}O{sub 7-{delta}} material. Then, critical magnetic field, critical current density and the jump in the specific heat at the critical temperature are calculated. Critical parameters are strongly affected by the doping with magnetic ions.

Electron plasma waves in CO/sub 2/ laser plasma interactions

International Nuclear Information System (INIS)

Baldis, H.A.; Villeneuve, D.M.; Walsh, C.J.

1984-01-01

During the past few years, the use of Thomson scattering in CO/sub 2/ laser produced plasmas has permitted the identification and study of electron plasma waves and ion waves, driven by various instabilities in the plasma corona, such as Stimulated Raman Scattering (SRS), two plasmon decay, and Stimulated Brillouin Scattering (SBS). Since these instabilities may coexist in the plasma, the density fluctuations associated with one wave may influence the behaviour of one or more of the other instabilities. The authors discuss the experimental evidence of such effects and, in particular, the consequences of a recent experiment in which the ion waves driven by SBS were observed to adversely affect the production of the electron plasma waves driven by SRS. In that experiment, a strong correlation was observed between the onset of SBS and the disappearance of the electron plasma waves driven by SRS at low densities (n/sub e/ n/sub e/ > 0.05 n/sub c/)

THz and Sub-THz Capabilities of a Table-Top Radiation Source Driven by an RF Thermionic Electron Gun

Energy Technology Data Exchange (ETDEWEB)

Smirnov, Alexei V.; Agustsson, R.; Boucher, S.; Campese, Tara; Chen, Y.C.; Hartzell, Josiah J.; Jocobson, B.T.; Murokh, A.; O' Shea, F.H.; Spranza, E.; Berg, W.; Borland, M.; Dooling, J. C.; Erwin, L.; Lindberg, R. R.; Pasky, S.J.; Sereno, N.; Sun, Y.; Zholents, A.

2017-06-01

Design features and experimental results are presented for a sub-mm wave source [1] based on APS RF thermionic electron gun. The setup includes compact alpha-magnet, quadrupoles, sub-mm-wave radiators, and THz optics. The sub-THz radiator is a planar, oversized structure with gratings. Source upgrade for generation frequencies above 1 THz is discussed. The THz radiator will use a short-period undulator having 1 T field amplitude, ~20 cm length, and integrated with a low-loss oversized waveguide. Both radiators are integrated with a miniature horn antenna and a small ~90°-degree in-vacuum bending magnet. The electron beamline is designed to operate different modes including conversion to a flat beam interacting efficiently with the radiator. The source can be used for cancer diagnostics, surface defectoscopy, and non-destructive testing. Sub-THz experiment demonstrated a good potential of a robust, table-top system for generation of a narrow bandwidth THz radiation. This setup can be considered as a prototype of a compact, laser-free, flexible source capable of generation of long trains of Sub-THz and THz pulses with repetition rates not available with laser-driven sources.

Magnetocaloric effect and critical behavior in melt-extracted Gd{sub 60}Co{sub 15}Al{sub 25} microwires

Energy Technology Data Exchange (ETDEWEB)

Xing, Dawei; Jiang, Sida; Chen, Dongming; Liu, Yanfen; Sun, Jianfei [School of Materials Science and Engineering, Harbin Institute of Technology (China); Shen, Hongxian [School of Materials Science and Engineering, Harbin Institute of Technology (China); Institute of Materials and Department of Physics, University of South Florida, Tampa, FL (United States); Liu, Jingshun [School of Materials Science and Engineering, Inner Mongolia University of Technology, Hohhot (China); Phan, Manh-Huong [Institute of Materials and Department of Physics, University of South Florida, Tampa, FL (United States); Wang, Huan; Qin, Faxiang [Institute for Composites Science and Innovation (InCSI), College of Materials Science and Engineering, Zhejiang University, Hangzhou (China)

2015-09-15

High-quality Gd{sub 60}Co{sub 15}Al{sub 25} microwires with an average diameter of 40 μm were successfully fabricated by the melt-extraction method. The as-cast microwires undergo a second-order paramagnetic to ferromagnetic (PM-FM) transition at ∝100 K. Large values of the magnetic entropy change (-ΔS{sub M} ∝9.73 J kg{sup -1} K{sup -1}) and the refrigerant capacity (RC ∝732 J kg{sup -1}) are achieved for a field change of 5 T. A careful analysis of critical exponents near the PM-FM transition indicates the significant effects of structural disorder on the long-range ferromagnetic interaction and the magnetocaloric response of the microwires. The excellent magnetocaloric properties make the Gd{sub 60}Co{sub 15}Al{sub 25} microwires very promising for use in magnetic refrigerators operating in the liquid nitrogen temperature range. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Ternary g-C{sub 3}N{sub 4}/Fe{sub 3}O{sub 4}/Ag{sub 3}VO{sub 4} nanocomposites: Novel magnetically separable visible-light-driven photocatalysts for efficiently degradation of dye pollutants

Energy Technology Data Exchange (ETDEWEB)

Mousavi, Mitra; Habibi-Yangjeh, Aziz, E-mail: ahabibi@uma.ac.ir

2015-08-01

In this work, novel magnetically separable g-C{sub 3}N{sub 4}/Fe{sub 3}O{sub 4}/Ag{sub 3}VO{sub 4} nanocomposites were successfully prepared by anchoring Fe{sub 3}O{sub 4} and Ag{sub 3}VO{sub 4} on surface of the g-C{sub 3}N{sub 4} sheets. The prepared samples were fairly characterized using X-ray diffraction, energy dispersive analysis of X-rays, scanning electron microscopy, transmission electron microscopy, UV–vis diffuse reflectance spectroscopy, photoluminescence spectroscopy, thermogravimetric analysis, and vibrating sample magnetometry techniques. Compared with the g-C{sub 3}N{sub 4} and g-C{sub 3}N{sub 4}/Fe{sub 3}O{sub 4} samples, the g-C{sub 3}N{sub 4}/Fe{sub 3}O{sub 4}/Ag{sub 3}VO{sub 4} nanocomposites displayed higher photocatalytic activity for degradation of rhodamine B under visible-light irradiation. Photocatalytic activity of the nanocomposite with 60% of Ag{sub 3}VO{sub 4} was about 14, 8, and 3-fold higher than those of the g-C{sub 3}N{sub 4}, g-C{sub 3}N{sub 4}/Fe{sub 3}O{sub 4}, and Ag{sub 3}VO{sub 4} samples, respectively. Furthermore, influence of refluxing time, calcination temperature, and scavengers of the reactive species on the degradation activity was investigated in detail and the results were discussed. The enhanced photocatalytic activity of the nanocomposites was attributed to efficiently separation of the charge carriers and their increased visible-light harvesting ability. - Graphical abstract: Display Omitted - Highlights: • g-C{sub 3}N{sub 4}/Fe{sub 3}O{sub 4}/Ag{sub 3}VO{sub 4} was prepared as ternary novel visible-light-driven photocatalyst. • Among the prepared samples, g-C{sub 3}N{sub 4}/Fe{sub 3}O{sub 4}/Ag{sub 3}VO{sub 4} (60%) has the best activity. • The activity was related to efficiently generation and separation of charge carriers. • The photocatalyst was magnetically separated from the treated solution.

Critical experiments at Sandia National Laboratories

International Nuclear Information System (INIS)

Harms, Gary A.; Ford, John T.; Barber, Allison Delo

2010-01-01

Sandia National Laboratories (SNL) has conducted radiation effects testing for the Department of Energy (DOE) and other contractors supporting the DOE since the 1960's. Over this period, the research reactor facilities at Sandia have had a primary mission to provide appropriate nuclear radiation environments for radiation testing and qualification of electronic components and other devices. The current generation of reactors includes the Annular Core Research Reactor (ACRR), a water-moderated pool-type reactor, fueled by elements constructed from UO2-BeO ceramic fuel pellets, and the Sandia Pulse Reactor III (SPR-III), a bare metal fast burst reactor utilizing a uranium-molybdenum alloy fuel. The SPR-III is currently defueled. The SPR Facility (SPRF) has hosted a series of critical experiments. A purpose-built critical experiment was first operated at the SPRF in the late 1980's. This experiment, called the Space Nuclear Thermal Propulsion Critical Experiment (CX), was designed to explore the reactor physics of a nuclear thermal rocket motor. This experiment was fueled with highly-enriched uranium carbide fuel in annular water-moderated fuel elements. The experiment program was completed and the fuel for the experiment was moved off-site. A second critical experiment, the Burnup Credit Critical Experiment (BUCCX) was operated at Sandia in 2002. The critical assembly for this experiment was based on the assembly used in the CX modified to accommodate low-enriched pin-type fuel in water moderator. This experiment was designed as a platform in which the reactivity effects of specific fission product poisons could be measured. Experiments were carried out on rhodium, an important fission product poison. The fuel and assembly hardware for the BUCCX remains at Sandia and is available for future experimentation. The critical experiment currently in operation at the SPRF is the Seven Percent Critical Experiment (7uPCX). This experiment is designed to provide benchmark

A novel visible light-driven Ag{sub 3}PO{sub 4}/SBA-15 nanocomposite: Preparation and application in the photo-degradation of pollutants

Energy Technology Data Exchange (ETDEWEB)

Chai, Yuanyuan; Wang, Li; Ren, Jia; Dai, Wei-Lin, E-mail: wldai@fudan.edu.cn

2015-01-01

Graphical abstract: - Highlights: • Highly efficient visible-light-driven Ag{sub 3}PO{sub 4}/SBA-15 nanocomposite. • Application in the photo-degradation of RhB. • Synthesis from a facile and simple colloidal method. • 20%-Ag{sub 3}PO{sub 4}/SBA-15 shows 8 times faster degradation rate than Ag{sub 3}PO{sub 4}. • Super stability and recycling ability. - Abstract: A novel visible light-driven environmental-benign Ag{sub 3}PO{sub 4}/SBA-15 nanocomposite photo-catalyst was synthesized for the photo-degradation of pollutants. The exploration on adsorption and photo-catalysis of dye or organic pollution for the nanocomposite was carried out. The adsorption capability for Ag{sub 3}PO{sub 4}/SBA-15 nanocomposite increases by 3 times compared with that of the Ag{sub 3}PO{sub 4} particles. The photo-catalytic activity of nanocomposite is higher than pristine Ag{sub 3}PO{sub 4} nanoparticle for the degradation of RhB or MO under visible light irradiation (λ > 420 nm). The effect of Ag{sub 3}PO{sub 4} loading on the catalytic performance was also studied. The results show that the optimum degradation is achieved over 20% Ag{sub 3}PO{sub 4}/SBA-15. Compared to pure Ag{sub 3}PO{sub 4} nanoparticle, the most efficient catalyst showed 8 times higher photo-catalytic activity for the degradation of RhB. The Ag{sub 3}PO{sub 4}/SBA-15 catalysts were systematically characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–Vis diffuse reflectance spectroscopy (DRS), and N{sub 2}-adsorption–desorption isotherms (BET). A possible mechanism scheme regarding photo-degradation enhancement induced by dye enrichments has been proposed on the Ag{sub 3}PO{sub 4}/SBA-15 nanocomposite. Additionally, the SBA-15 support can enhance the efficiency of separation of catalyst from the reaction mixture, implying that the Ag{sub 3}PO{sub 4} loading on the SBA-15 catalyst will not result in the extra environment and health

Internal transport barriers: critical physics issues?

Energy Technology Data Exchange (ETDEWEB)

Litaudon, X [Association Euratom-CEA, DSM, Departement de Recherches sur La Fusion Controlee, Centre d' Etudes de Cadarache, F-13108 Saint-Paul-Lez-Durance (France)

2006-05-15

Plasmas regimes with improved core energy confinement properties, i.e. with internal transport barriers (ITB), provide a possible route towards simultaneous high fusion performance and continuous tokamak reactor operation in a non-inductive current drive state. High core confinement regimes should be made compatible with a dominant fraction of the plasma current self-generated (pressure-driven) by the bootstrap effect while operating at high normalized pressure and moderate current. Furthermore, ITB regimes with 'non-stiff' plasma core pressure break the link observed in standard inductive operation between fusion performances and plasma pressure at the edge, thus offering a new degree of freedom in the tokamak operational space. Prospects and critical issues for using plasmas with enhanced thermal core insulation as a basis for steady tokamak reactor operation are reviewed in the light of the encouraging experimental and modelling results obtained recently (typically in the last two years). An extensive set of data from experiments carried out worldwide has been gathered on ITB regimes covering a wide range of parameters (q-profile, T{sub i}/T{sub e}, gradient length, shaping, normalized toroidal Larmor radius, collisionality, Mach number, etc). In the light of the progress made recently, the following critical physics issues relevant to the extrapolation of ITB regimes to next-step experiments, such as ITER, are addressed: 1. conditions for ITB formation and existence of a power threshold,; 2. ITB sustainment at T{sub i} {approx} T{sub e}, with low toroidal torque injection, low central particle fuelling but at high density and low impurity concentration,; 3. control of confinement for sustaining wide ITBs that encompass a large volume at high {beta}{sub N},; 4. real time profile control (q and pressure) with high bootstrap current and large fraction of alpha-heating and; 5. compatibility of core with edge transport barriers or with external core

Critical dynamics and domain motion from permittivity of the electronic ferroelectric (TMTTF){sub 2}AsF{sub 6}

Energy Technology Data Exchange (ETDEWEB)

Brazovskii, Serguei, E-mail: brazov@lptms.u-psud.fr [LPTMS, UMR8626, CNRS & University Paris-Sud, Bat. 100, Orsay F-91405 (France); International Institute of Physics, 59078-400 Natal, Rio Grande do Norte (Brazil); Monceau, Pierre [CNRS & University Grenoble Alpes, Institute NEEL, F-38042 Grenoble (France); Nad, Felix Ya.

2015-03-01

The quasi one-dimensional organic conductor (TMTTF){sub 2}AsF{sub 6} shows the charge ordering transition at T{sub CO}=101 K to a state of the ferroelectric Mott insulator which is still well conducting. We present and interpret the experimental data on the gigantic dielectric response in the vicinity of T{sub CO}, concentrating on the frequency dependence of the inverse 1/ε of the complex permittivity ε=ε′+iε′′. Surprisingly for a ferroelectric, we could closely approach the 2nd order phase transition and to deeply reach the critical dynamics of the polarization. We could analyze the critical slowing-down when approaching T{sub CO} from both sides and to extract the anomalous power law for the frequency dependence of the order parameter viscosity. Moreover, below T{sub CO} we could extract a sharp absorption feature coming from a motion of domain walls which shows up at a frequency well below the relaxation rate.

Improvement of critical current density in thallium-based (Tl,Bi)Sr{sub 1.6}Ba{sub 0.4}Ca{sub 2}Cu{sub 3}O{sub x} superconductors

Energy Technology Data Exchange (ETDEWEB)

Ren, Z.F.; Wang, C.A.; Wang, J.H. [State Univ. of New York at Buffalo, Amherst, NY (United States)] [and others

1994-12-31

Epitaxial (Tl,Bi)Sr{sub 1.6}Ba{sub 0.4}Ca{sub 2}Cu{sub 3}O{sub x} (Tl,Bi)-1223 thin films on (100) single crystal LaAlO{sub 3} substrates were synthesized by a two-step procedure. Phase development, microstructure, and relationships between film and substrate were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Resistance versus temperature, zero-field-cooled and field-cooled magnetization, and transport critical current density (J{sub c}) were measured. The zero-resistance temperature was 105-111 K. J{sub c} at 77 K and zero field was > 2 x 10{sup 6} A/cm{sup 2}. The films exhibited good flux pinning properties.

IAEA coordinated research project (CRP) on 'Analytical and experimental benchmark analyses of accelerator driven systems'

International Nuclear Information System (INIS)

Abanades, Alberto; Aliberti, Gerardo; Gohar, Yousry; Talamo, Alberto; Bornos, Victor; Kiyavitskaya, Anna; Carta, Mario; Janczyszyn, Jerzy; Maiorino, Jose; Pyeon, Cheolho; Stanculescu, Alexander; Titarenko, Yury; Westmeier, Wolfram

2008-01-01

In December 2005, the International Atomic Energy Agency (IAEA) has started a Coordinated Research Project (CRP) on 'Analytical and Experimental Benchmark Analyses of Accelerator Driven Systems'. The overall objective of the CRP, performed within the framework of the Technical Working Group on Fast Reactors (TWGFR) of IAEA's Nuclear Energy Department, is to increase the capability of interested Member States in developing and applying advanced reactor technologies in the area of long-lived radioactive waste utilization and transmutation. The specific objective of the CRP is to improve the present understanding of the coupling of an external neutron source (e.g. spallation source) with a multiplicative sub-critical core. The participants are performing computational and experimental benchmark analyses using integrated calculation schemes and simulation methods. The CRP aims at integrating some of the planned experimental demonstration projects of the coupling between a sub-critical core and an external neutron source (e.g. YALINA Booster in Belarus, and Kyoto University's Critical Assembly (KUCA)). The objective of these experimental programs is to validate computational methods, obtain high energy nuclear data, characterize the performance of sub-critical assemblies driven by external sources, and to develop and improve techniques for sub-criticality monitoring. The paper summarizes preliminary results obtained to-date for some of the CRP benchmarks. (authors)

Critical experiments at Sandia National Laboratories

International Nuclear Information System (INIS)

Harms, G.A.; Ford, J.T.; Barber, A.D.

2011-01-01

Sandia National Laboratories (SNL) has conducted radiation effects testing for the Department of Energy (DOE) and other contractors supporting the DOE since the 1960's. Over this period, the research reactor facilities at Sandia have had a primary mission to provide appropriate nuclear radiation environments for radiation testing and qualification of electronic components and other devices. The current generation of reactors includes the Annular Core Research Reactor (ACRR), a water-moderated pool-type reactor, fueled by elements constructed from UO2-BeO ceramic fuel pellets, and the Sandia Pulse Reactor III (SPR-III), a bare metal fast burst reactor utilizing a uranium-molybdenum alloy fuel. The SPR-III is currently defueled. The SPR Facility (SPRF) has hosted a series of critical experiments. A purpose-built critical experiment was first operated at the SPRF in the late 1980's. This experiment, called the Space Nuclear Thermal Propulsion Critical Experiment (CX), was designed to explore the reactor physics of a nuclear thermal rocket motor. This experiment was fueled with highly-enriched uranium carbide fuel in annular water-moderated fuel elements. The experiment program was completed and the fuel for the experiment was moved off-site. A second critical experiment, the Burnup Credit Critical Experiment (BUCCX) was operated at Sandia in 2002. The critical assembly for this experiment was based on the assembly used in the CX modified to accommodate low-enriched pin-type fuel in water moderator. This experiment was designed as a platform in which the reactivity effects of specific fission product poisons could be measured. Experiments were carried out on rhodium, an important fission product poison. The fuel and assembly hardware for the BUCCX remains at Sandia and is available for future experimentation. The critical experiment currently in operation at the SPRF is the Seven Percent Critical Experiment (7uPCX). This experiment is designed to provide benchmark

Critical experiments at Sandia National Laboratories

Energy Technology Data Exchange (ETDEWEB)

Harms, G.A.; Ford, J.T.; Barber, A.D., E-mail: gaharms@sandia.gov [Sandia National Laboratories, Albuquerque, NM (United States)

2011-07-01

Sandia National Laboratories (SNL) has conducted radiation effects testing for the Department of Energy (DOE) and other contractors supporting the DOE since the 1960's. Over this period, the research reactor facilities at Sandia have had a primary mission to provide appropriate nuclear radiation environments for radiation testing and qualification of electronic components and other devices. The current generation of reactors includes the Annular Core Research Reactor (ACRR), a water-moderated pool-type reactor, fueled by elements constructed from UO2-BeO ceramic fuel pellets, and the Sandia Pulse Reactor III (SPR-III), a bare metal fast burst reactor utilizing a uranium-molybdenum alloy fuel. The SPR-III is currently defueled. The SPR Facility (SPRF) has hosted a series of critical experiments. A purpose-built critical experiment was first operated at the SPRF in the late 1980's. This experiment, called the Space Nuclear Thermal Propulsion Critical Experiment (CX), was designed to explore the reactor physics of a nuclear thermal rocket motor. This experiment was fueled with highly-enriched uranium carbide fuel in annular water-moderated fuel elements. The experiment program was completed and the fuel for the experiment was moved off-site. A second critical experiment, the Burnup Credit Critical Experiment (BUCCX) was operated at Sandia in 2002. The critical assembly for this experiment was based on the assembly used in the CX modified to accommodate low-enriched pin-type fuel in water moderator. This experiment was designed as a platform in which the reactivity effects of specific fission product poisons could be measured. Experiments were carried out on rhodium, an important fission product poison. The fuel and assembly hardware for the BUCCX remains at Sandia and is available for future experimentation. The critical experiment currently in operation at the SPRF is the Seven Percent Critical Experiment (7uPCX). This experiment is designed to provide

Monte Carlo study of the critical behavior and magnetic properties of La{sub 2/3}Ca{sub 1/3}MnO{sub 3} thin films

Energy Technology Data Exchange (ETDEWEB)

Restrepo-Parra, E., E-mail: erestrepopa@unal.edu.c [Departamento de Fisica y Quimica, Universidad Nacional de Colombia-Sede Manizales, A.A. 127 Manizales (Colombia); Bedoya-Hincapie, C.M.; Jurado, F.J.; Riano-Rojas, J.C. [Departamento de Fisica y Quimica, Universidad Nacional de Colombia-Sede Manizales, A.A. 127 Manizales (Colombia); Restrepo, J. [Grupo de Magnetismo y Simulacion G, Instituto de Fisica, Universidad de Antioquia, A.A. 1226 Medellin (Colombia)

2010-11-15

Critical exponents offer important information concerning the interaction mechanisms near the paramagnetic to ferromagnetic transition. In this work a Monte Carlo-Metropolis simulation of the critical behavior in La{sub 2/3}Ca{sub 1/3}MnO{sub 3} thin films is addressed. Canonical ensemble averages for magnetization per site, magnetic susceptibility and specific heat of stoichiometric manganite within a three-dimensional classical Heisenberg model with nearest magnetic neighbor interactions are computed. The La{sub 2/3}Ca{sub 1/3}MnO{sub 3} thin films were simulated addressing the thickness influence and thermal dependence. In the model, Mn magnetic ions are distributed on a simple cubic lattice according to the perovskite structure of this manganite. Ferromagnetic coupling for the bonds Mn{sup 3+}-Mn{sup 3+}(e{sub g}-e{sub g}'), Mn{sup 3+}-Mn{sup 4+}(e{sub g}-d{sup 3}) and Mn{sup 3+}-Mn{sup 4+}(e{sub g}'-d{sup 3}) were taken into account. On the basis of finite-size scaling theory, our best estimates of critical exponents, linked to the ferromagnetic to paramagnetic transition, for the correlation length, specific heat, magnetization and susceptibility are, respectively: v=0.56{+-}0.01, {alpha}=0.16{+-}0.03, {beta}=0.34{+-}0.04{gamma} and {gamma}=1.17{+-}0.05. These theoretical results are consistent with the Rushbrooke equalitiy {alpha}+2{beta}+{gamma}=2.

Kinematics and dynamics of salt movement driven by sub-salt normal faulting and supra-salt sediment accumulation - combined analogue experiments and analytical calculations

Science.gov (United States)

Warsitzka, Michael; Kukowski, Nina; Kley, Jonas

2017-04-01

In extensional sedimentary basins, the movement of ductile salt is mainly controlled by the vertical displacement of the salt layer, differential loading due to syn-kinematic deposition, and tectonic shearing at the top and the base of the salt layer. During basement normal faulting, salt either tends to flow downward to the basin centre driven by its own weight or it is squeezed upward due to differential loading. In analogue experiments and analytical models, we address the interplay between normal faulting of the sub-salt basement, compaction and density inversion of the supra-salt cover and the kinematic response of the ductile salt layer. The analogue experiments consist of a ductile substratum (silicone putty) beneath a denser cover layer (sand mixture). Both layers are displaced by normal faults mimicked through a downward moving block within the rigid base of the experimental apparatus and the resulting flow patterns in the ductile layer are monitored and analysed. In the computational models using an analytical approximative solution of the Navier-Stokes equation, the steady-state flow velocity in an idealized natural salt layer is calculated in order to evaluate how flow patterns observed in the analogue experiments can be translated to nature. The analytical calculations provide estimations of the prevailing direction and velocity of salt flow above a sub-salt normal fault. The results of both modelling approaches show that under most geological conditions salt moves downwards to the hanging wall side as long as vertical offset and compaction of the cover layer are small. As soon as an effective average density of the cover is exceeded, the direction of the flow velocity reverses and the viscous material is squeezed towards the elevated footwall side. The analytical models reveal that upward flow occurs even if the average density of the overburden does not exceed the density of salt. By testing various scenarios with different layer thicknesses

Layer structured Na{sub 2}Ni(MoO{sub 4}){sub 2} particles as a visible-light-driven photocatalyst for degradation of methylene blue

Energy Technology Data Exchange (ETDEWEB)

Lu, Yuting; Chen, Luyang; Huang, Yanlin [College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123 (China); Chen, Cuili; Kim, Sun Il [Department of Physics and Interdisciplinary Program of Biomedical, Mechanical & Electrical Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of); Seo, Hyo Jin, E-mail: hjseo@pknu.ac.kr [Department of Physics and Interdisciplinary Program of Biomedical, Mechanical & Electrical Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of)

2015-03-15

Highlights: • Na{sub 2}Ni(MoO{sub 4}){sub 2} nanoparticles were developed by Pechini method. • The nanoparticles show high absorption in UV–vis wavelength region. • Na{sub 2}Ni(MoO{sub 4}){sub 2} has high activity in the MB dye degradation under visible light. • Hexagonal layers with heavily distorted NiO{sub 6} were superiority for photocatalysis. - Abstract: A new visible-light-driven photocatalyst of Na{sub 2}Ni(MoO{sub 4}){sub 2} particle was prepared by the modified Pechini method. The crystal structure was measured by X-ray diffraction (XRD) and the structural refinement. The sample was investigated by scanning electron microscope (SEM), transmission electron microscopy (TEM), and UV–vis absorption spectrum measurements. The average size of Na{sub 2}Ni(MoO{sub 4}){sub 2} particle is about 180 nm. Na{sub 2}Ni(MoO{sub 4}){sub 2} particle have an efficient optical absorption in the UV–visible light wavelength region with a direct allowed electronic transition of 2.06 eV. The effective photodegradation of methylene blue (MB) dye was demonstrated, which benefits from the special crystal structure of Na{sub 2}Ni(MoO{sub 4}){sub 2} particle. This crystal lattice has two infinite chains formed by (Ni,Na)O{sub 6} and MoO{sub 4} polyhedra standing in lines alone with the inner wall of the hexagonal tunnels. This results in the efficient optical absorption and provides more chances for electron–hole separations, which can further react with dye molecules to oxidize the dye pollutant into non-toxic products.

Critical end point of the first-order ferromagnetic transition in a Sm{sub 0.55}(Sr{sub 0.5}Ca{sub 0.5}){sub 0.45}MnO{sub 3} single crystal

Energy Technology Data Exchange (ETDEWEB)

Radheep, D. Mohan [Centre for High Pressure Research, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India); Sarkar, P. [Department of Physics, Serampore College, Serampore 712 201 (India); Arumugam, S. [Centre for High Pressure Research, School of Physics, Bharathidasan University, Tiruchirappalli 620 024 (India); Suryanarayanan, R. [Laboratoire de Physico-Chimie de l' Etat Solide, ICMMO, CNRS, UMR8182, Universite Paris-Sud, 91405 Orsay (France); Mandal, P., E-mail: prabhat.mandal@saha.ac.in [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Calcutta 700 064 (India)

2014-09-01

We report on the magnetic field (H) and hydrostatic pressure (P) dependence of the order of the ferromagnetic (FM) to paramagnetic phase transition in a Sm{sub 0.55}(Sr{sub 0.5}Ca{sub 0.5}){sub 0.45}MnO{sub 3} single crystal. At ambient condition, the system exhibits a first-order FM transition at T{sub C}≈82K (in heating cycle) with strong thermal hysteresis (∼13 K). The application of external H and P increases T{sub C}, suppresses the hysteresis width, and thus weakens the first-order nature of the transition. Our analysis reveals that the hysteresis vanishes and the first-order FM transition becomes a crossover above a critical magnetic field H{sub cr}≈11.5T. The value of H{sub cr} is highest among the manganite family, although the first-order nature of the FM transition is believed to be strongest in Eu{sub 1−x}Sr{sub x}MnO{sub 3}(x≈0.45). - Highlights: • System shows a strong first-order ferromagnetic to paramagnetic phase transition. • Extremely sharp metal–insulator transition at around 82 K. • The value of critical magnetic field at which first-order transition becomes a crossover is highest among manganites. • The nature of transition is sensitive to external perturbations such as magnetic field and pressure.

Calculational study of benchmark critical experiments on high-enriched uranyl nitrate solution systems

International Nuclear Information System (INIS)

Oh, I.; Rothe, R.E.

1978-01-01

Criticality calculations on minimally reflected, concrete-reflected, and plastic-reflected single tanks and on arrays of cylinders reflected by concrete and plastic have been performed using the KENO-IV code with 16-group Hansen-Roach neutron cross sections. The fissile material was high-enriched (93.17% 235 U) uranyl nitrate [UO 2 (NO 3 ) 2 ] solution. Calculated results are compared with those from a benchmark critical experiments program to provide the best possible verification of the calculational technique. The calculated k/sub eff/'s underestimate the critical condition by an average of 1.28% for the minimally reflected single tanks, 1.09% for the concrete-reflected single tanks, 0.60% for the plastic-reflected single tanks, 0.75% for the concrete-reflected arrays of cylinders, and 0.51% for the plastic-reflected arrays of cylinders. More than half of the present comparisons were within 1% of the experimental values, and the worst calculational and experimental discrepancy was 2.3% in k/sub eff/ for the KENO calculations

Avalanches and Criticality in Driven Magnetic Skyrmions

Science.gov (United States)

Díaz, S. A.; Reichhardt, C.; Arovas, D. P.; Saxena, A.; Reichhardt, C. J. O.

2018-03-01

We show using numerical simulations that slowly driven Skyrmions interacting with random pinning move via correlated jumps or avalanches. The avalanches exhibit power-law distributions in their duration and size, and the average avalanche shape for different avalanche durations can be scaled to a universal function, in agreement with theoretical predictions for systems in a nonequilibrium critical state. A distinctive feature of Skyrmions is the influence of the nondissipative Magnus term. When we increase the ratio of the Magnus term to the damping term, a change in the universality class of the behavior occurs, the average avalanche shape becomes increasingly asymmetric, and individual avalanches exhibit motion in the direction perpendicular to their own density gradient.

Fast accelerator driven subcritical system for energy production: nuclear fuel evolution

International Nuclear Information System (INIS)

Barros, Graiciany de P.; Pereira, Claubia; Veloso, Maria A.F.; Costa, Antonella L.

2011-01-01

Accelerators Driven Systems (ADS) are an innovative type of nuclear system, which is useful for long-lived fission product transmutation and fuel regeneration. The ADS consist of a coupling of a sub-critical nuclear core reactor and a proton beam produced by a particle accelerator. These particles are injected into a target for the neutrons production by spallation reactions. The neutrons are then used to maintain the fission chain in the sub-critical core. The aim of this study is to investigate the nuclear fuel evolution of a lead cooled accelerator driven system used for energy production. The fuel studied is a mixture based upon "2"3"2Th and "2"3"3U. Since thorium is an abundant fertile material, there is hope for the thorium-cycle fuels for an accelerator driven sub-critical system. The target is a lead spallation target and the core is filled with a hexagonal lattice. High energy neutrons are used to reduce the negative reactivity caused by the presence of protoactinium, since this effect is most pronounced in the thermal range of the neutron spectrum. For that reason, such material is not added moderator to the system. In this work is used the Monte Carlo code MCNPX 2.6.0, that presents the the depletion/ burnup capability. The k_e_f_f evolution, the neutron energy spectrum in the core and the nuclear fuel evolution using ADS source (SDEF) and kcode-mode are evaluated during the burnup. (author)

Locative media and data-driven computing experiments

Directory of Open Access Journals (Sweden)

Sung-Yueh Perng

2016-06-01

Full Text Available Over the past two decades urban social life has undergone a rapid and pervasive geocoding, becoming mediated, augmented and anticipated by location-sensitive technologies and services that generate and utilise big, personal, locative data. The production of these data has prompted the development of exploratory data-driven computing experiments that seek to find ways to extract value and insight from them. These projects often start from the data, rather than from a question or theory, and try to imagine and identify their potential utility. In this paper, we explore the desires and mechanics of data-driven computing experiments. We demonstrate how both locative media data and computing experiments are ‘staged’ to create new values and computing techniques, which in turn are used to try and derive possible futures that are ridden with unintended consequences. We argue that using computing experiments to imagine potential urban futures produces effects that often have little to do with creating new urban practices. Instead, these experiments promote Big Data science and the prospect that data produced for one purpose can be recast for another and act as alternative mechanisms of envisioning urban futures.

Analytical results on the periodically driven damped pendulum. Application to sliding charge-density waves and Josephson junctions

International Nuclear Information System (INIS)

Azbel, M.Y.; Bak, P.

1984-01-01

The differential equation epsilonphi-dieresis+phi-dot-(1/2)α sin(2phi) = I+summation/sub n/ = -infinity/sup infinity/A/sub n/delta(t-t/sub n/) describing the periodically driven damped pendulum is analyzed in the strong damping limit epsilon<<1, using first-order perturbation theory. The equation may represent the motion of a sliding charge-density wave (CDW) in ac plus dc electric fields, and the resistively shunted Josephson junction driven by dc and microwave currents. When the torque I exceeds a critical value the pendulum rotates with a frequency ω. For infinite damping, or zero mass (epsilon = 0), the equation can be transformed to the Schroedinger equation of the Kronig-Penney model. When A/sub n/ is random the pendulum exhibits chaotic motion. In the regular case A/sub n/ = A the frequency ω is a smooth function of the parameters, so there are no phase-locked subharmonic plateaus in the ω(I) curve, or the I-V characteristics for the CDW or Josephson-junction systems. For small nonzero epsilon the return map expressing the phase phi(t/sub n/+1) as a function of the phase phi(t/sub n/) is a one-dimensional circle map. Applying known analytical results for the circle map one finds narrow subharmonic plateaus at all rational frequencies, in agreement with experiments on CDW systems

AWAKE, The Advanced Proton Driven Plasma Wakefield Acceleration Experiment at CERN

CERN Document Server

Gschwendtner, E.; Amorim, L.; Apsimon, R.; Assmann, R.; Bachmann, A.M.; Batsch, F.; Bauche, J.; Berglyd Olsen, V.K.; Bernardini, M.; Bingham, R.; Biskup, B.; Bohl, T.; Bracco, C.; Burrows, P.N.; Burt, G.; Buttenschon, B.; Butterworth, A.; Caldwell, A.; Cascella, M.; Chevallay, E.; Cipiccia, S.; Damerau, H.; Deacon, L.; Dirksen, P.; Doebert, S.; Dorda, U.; Farmer, J.; Fedosseev, V.; Feldbaumer, E.; Fiorito, R.; Fonseca, R.; Friebel, F.; Gorn, A.A.; Grulke, O.; Hansen, J.; Hessler, C.; Hofle, W.; Holloway, J.; Huther, M.; Jaroszynski, D.; Jensen, L.; Jolly, S.; Joulaei, A.; Kasim, M.; Keeble, F.; Li, Y.; Liu, S.; Lopes, N.; Lotov, K.V.; Mandry, S.; Martorelli, R.; Martyanov, M.; Mazzoni, S.; Mete, O.; Minakov, V.A.; Mitchell, J.; Moody, J.; Muggli, P.; Najmudin, Z.; Norreys, P.; Oz, E.; Pardons, A.; Pepitone, K.; Petrenko, A.; Plyushchev, G.; Pukhov, A.; Rieger, K.; Ruhl, H.; Salveter, F.; Savard, N.; Schmidt, J.; Seryi, A.; Shaposhnikova, E.; Sheng, Z.M.; Sherwood, P.; Silva, L.; Soby, L.; Sosedkin, A.P.; Spitsyn, R.I.; Trines, R.; Tuev, P.V.; Turner, M.; Verzilov, V.; Vieira, J.; Vincke, H.; Wei, Y.; Welsch, C.P.; Wing, M.; Xia, G.; Zhang, H.

2016-01-01

The Advanced Proton Driven Plasma Wakefield Acceleration Experiment (AWAKE) aims at studying plasma wakefield generation and electron acceleration driven by proton bunches. It is a proof-of-principle R&D experiment at CERN and the world's first proton driven plasma wakefield acceleration experiment. The AWAKE experiment will be installed in the former CNGS facility and uses the 400 GeV/c proton beam bunches from the SPS. The first experiments will focus on the self-modulation instability of the long (rms ~12 cm) proton bunch in the plasma. These experiments are planned for the end of 2016. Later, in 2017/2018, low energy (~15 MeV) electrons will be externally injected to sample the wakefields and be accelerated beyond 1 GeV. The main goals of the experiment will be summarized. A summary of the AWAKE design and construction status will be presented.

Characterization of neutron leakage probability, k /SUB eff/ , and critical core surface mass density of small reactor assemblies through the Trombay criticality formula

International Nuclear Information System (INIS)

Kumar, A.; Rao, K.S.; Srinivasan, M.

1983-01-01

The Trombay criticality formula (TCF) has been derived by incorporating a number of well-known concepts of criticality physics to enable prediction of changes in critical size or k /SUB eff/ following alterations in geometrical and physical parameters of uniformly reflected small reactor assemblies characterized by large neutron leakage from the core. The variant parameters considered are size, shape, density and diluent concentration of the core, and density and thickness of the reflector. The effect of these changes (except core size) manifests, through sigma /SUB c/ the critical surface mass density of the ''corresponding critical core,'' that sigma, the massto-surface-area ratio of the core,'' is essentially a measure of the product /rho/ extended to nonspherical systems and plays a dominant role in the TCF. The functional dependence of k /SUB eff/ on sigma/sigma /SUB c/ , the system size relative to critical, is expressed in the TCF through two alternative representations, namely the modified Wigner rational form and, an exponential form, which is given

Search for {nu}{sub {mu}}{yields}{nu}{sub e} oscillations in the NOMAD experiment; Recherche des oscillations {nu}{sub {mu}}{yields}{nu}{sub e} dans l'experience NOMAD

Energy Technology Data Exchange (ETDEWEB)

Krasnoperov, A

2000-06-01

The NOMAD experiment is looking for {nu}{sub {mu}}{yields}{nu}{sub {tau}} and {nu}{yields}{nu}{sub e} oscillations in a predominantly {nu}{sub {mu}} beam at the CERN SPS. Neutrino oscillations are closely related with the existence of non-zero neutrino mass and mixing between different flavours. This document describes the search for {nu}{sub {mu}}{yields}{nu}{sub e} oscillations in the full NOMAD data sample accumulated during four years of data-taking (1995-98). The search for {nu}{sub e} appearance was performed by studying the charged current (CC) interactions with in the NOMAD detector. The selection of {nu}{sub e} CC and {nu}{sub {mu}} interactions with the help of different particle identification algorithms, as well as using the event kinematic criteria, is described here in detail. We show that the NOMAD experiment is sensitive to the LSND allowed region of oscillation parameters with the squared mass difference larger than 10 eV{sup 2}/C{sup 4}. An upper limit on the probability of {nu}{sub {mu}}{yields}{nu}{sub e} oscillations, based on a fraction of the NOMAD data, is given. (author)

Towards a conceptual framework for Experience-Driven Innovation

NARCIS (Netherlands)

Schifferstein, H.N.J.; Kleinsmann, M.S.; Jepma, E.J.

2012-01-01

Companies that aim to evoke specific experiences among their customers, should not only modify their design process, but also need to reorganize their innovation processes. Experience-driven innovation has implications on at least three levels in the organization: company, brand, and product/service

Completion of the first approach to critical for the seven percent critical experiment

International Nuclear Information System (INIS)

Barber, A. D.; Harms, G. A.

2009-01-01

The first approach-to-critical experiment in the Seven Percent Critical Experiment series was recently completed at Sandia. This experiment is part of the Seven Percent Critical Experiment which will provide new critical and reactor physics benchmarks for fuel enrichments greater than five weight percent. The inverse multiplication method was used to determine the state of the system during the course of the experiment. Using the inverse multiplication method, it was determined that the critical experiment went slightly supercritical with 1148 fuel elements in the fuel array. The experiment is described and the results of the experiment are presented. (authors)

Modeling of laser-driven hydrodynamics experiments

Science.gov (United States)

di Stefano, Carlos; Doss, Forrest; Rasmus, Alex; Flippo, Kirk; Desjardins, Tiffany; Merritt, Elizabeth; Kline, John; Hager, Jon; Bradley, Paul

2017-10-01

Correct interpretation of hydrodynamics experiments driven by a laser-produced shock depends strongly on an understanding of the time-dependent effect of the irradiation conditions on the flow. In this talk, we discuss the modeling of such experiments using the RAGE radiation-hydrodynamics code. The focus is an instability experiment consisting of a period of relatively-steady shock conditions in which the Richtmyer-Meshkov process dominates, followed by a period of decaying flow conditions, in which the dominant growth process changes to Rayleigh-Taylor instability. The use of a laser model is essential for capturing the transition. also University of Michigan.

Instability and transport driven by an electron temperature gradient close to critical

International Nuclear Information System (INIS)

Dong, J.Q.; Jian, G.D.; Wang, A.K.; Sanuki, H.; Itoh, K.

2003-01-01

Electron temperature gradient (ETG) driven instability in toroidal plasmas is studied with gyrokinetic theory. The full electron kinetics is considered. The upgraded numerical scheme for solving the integral eigenvalue equations allows the study of both growing and damping modes, and thus direct calculation of critical gradient. Algebraic formulas for the critical gradient with respect to ratio of electron temperature over ion temperature and to toroidicity are given. An estimation for turbulence induced transport is presented. (author)

Experimental subcritical facility driven by D-D/D-T neutron generator at BARC, India

Energy Technology Data Exchange (ETDEWEB)

Sinha, Amar, E-mail: image@barc.gov.in; Roy, Tushar; Kashyap, Yogesh; Ray, Nirmal; Shukla, Mayank; Patel, Tarun; Bajpai, Shefali; Sarkar, P.S.; Bishnoi, Saroj

2015-05-01

Highlights: •Experimental subcritical facility BRAHMMA coupled to D-D/D-T neutron generator. •Preliminary results of PNS experiments reported. •Feynman-alpha noise measurements explored with continuous source. -- Abstract: The paper presents design of an experimental subcritical assembly driven by D-D/D-T neutron and preliminary experimental measurements. The system has been developed for investigating the static and dynamic neutronic properties of accelerator driven sub-critical systems. This system is modular in design and it is first in the series of subcritical assemblies being designed. The subcritical core consists of natural uranium fuel with high density polyethylene as moderator and beryllium oxide as reflector. The fuel is embedded in high density polyethylene moderator matrix. Estimated k{sub eff} of the system is ∼0.89. One of the unique features of subcritical core is the use of Beryllium oxide (BeO) as reflector and HDPE as moderator making the assembly a compact modular system. The subcritical core is coupled to Purnima Neutron Generator which works in D-D and D-T mode with both DC and pulsed operation. It has facility for online source strength monitoring using neutron tagging and programmable source modulation. Preliminary experiments have been carried out for spatial flux measurement and reactivity estimation using pulsed neutron source (PNS) techniques with D-D neutrons. Further experiments are being planned to measure the reactivity and other kinetic parameters using noise methods. This facility would also be used for carrying out studies on effect of source importance and measurement of source multiplication factor k{sub s} and external neutron source efficiency φ{sup ∗} in great details. Experiments with D-T neutrons are also underway.

Critical experiments AT Pacific Northwest Laboratory

International Nuclear Information System (INIS)

Clayton, E.D.; Bierman, S.R.

1984-01-01

After a short description of the facility, a brief listing of the principal types of fuel forms and assembly geometries is provided. A number of experiments have recently been performed on plain fissionable units, or isolated assemblies of single units, that include measurements on solutions composed of Pu-U mixtures and critical experiment data on lattices of low enriched uranium in water. Experiments have been performed on planar arrays of containers with Pu solutions because of the lack of data in this field concerning the safe storage of nuclear fuel; others have been conducted on arrays of low enriched U lattice assemblies. Neutronic measurements to date have shown they can be used to provide additional benchmark data for improvement and validation of criticality codes. Studies have previously been made to ascertain the need for critical experiments in support of fuel recycle operations. The result of an effort to update the list of needed critical experiments is summarized in this section. Experiments are listed in support of uranium based fuels and fast breeder reactor fuels. An effort is made to identify those areas within the fuel cycle wherein the critical experiment data would be applied and to identify the experiments (and data) required to fulfill the needs in each of these areas. The type and form of fuel on which the data would be obtained also are identified. In presenting this information, no attempt is made to describe the experiments in detail, or to define the actual number of critical experiments that might be needed to provide the required data

A study of parameter setting and characterization of visible-light driven nitrogen-modified commercial TiO{sub 2} photocatalysts

Energy Technology Data Exchange (ETDEWEB)

Kuo, Yu-Lin, E-mail: ylkuo@mail.ntust.edu.tw [Department of Mechanical Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei 106, Taiwan (China); Su, Te-Li [Department of Cosmetic Application and Management, St. Mary' s Medicine, Nursing and Management College, Yilan 266, Taiwan (China); Kung, Fu-Chen [Department of Health Developing and Health Marketing, Kainan University, Taoyuan County 338, Taiwan (China); Wu, Tsai-Jung [Department of Mechanical Engineering, National Taiwan University of Science and Technology, No. 43, Sec. 4, Keelung Rd., Taipei 106, Taiwan (China)

2011-06-15

Highlights: {yields} A cost-effective and highly-efficient visible-light driven nitrogen-modified TiO{sub 2} photocatalyst was prepared by a simple hydrolysis method. {yields} The obtained optimum conditions applied to Taguchi method for preparing visible-light driven photocatalyst were undergone by the process of stirring for 1 day using 4M ammonium as the nitrogen source, and then calcining at 400{sup Degree-Sign }C for 2 h. {yields} Several materials technologies of characterizing N-TiO2 photocatalyst have been used to realize the modification of TiO2 by ammonia water as the nitrogen source. - Abstract: An optimal condition applied to the Taguchi method with an L{sub 9} orthogonal array for preparing a visible-light driven nitrogen-modified TiO{sub 2} (N-TiO{sub 2}) photocatalyst by a simple hydrolysis method has been examined for material characteristics and a photodecolorization test of methyl blue (MB) under various visible light source (fluorescent and blue LED lamps) irradiations. Results of the material characterization showed that the absorption of prepared N-TiO{sub 2} powder exhibited a significant extension into visible light regimes with an optical bandgap (Eg) of around 2.96 eV, which subsequently improved the visible-light photocatalytic activity of N-TiO{sub 2} samples. The superior photocatalytic properties, the pseudo first-order reaction rate constants (k) and photodecolorization efficiency ({eta}%) of a N-TiO{sub 2} photocatalyst during the photodecolorization test of methyl blue (MB) under two different visible light irradiations were very evident compared to those for pure TiO{sub 2}. For photodecolorization of practical dyeing from the waste water from the dyeing and finishing industry, a higher photodecolorization efficiency of N-TiO{sub 2} powder toward Direct blue-86 (DB-86) (Direct Fast Turquoise Blue GL) dye was also achieved.

Etching of LiNbO/sub 3/ by laser-driven fusion of salts

International Nuclear Information System (INIS)

Ashby, C.I.H.; Brannon, P.J.

1987-01-01

Lithium niobate exhibits low reactivity with most chemical etchants. Consequently, etching a LiNbO/sub 3/ surface to produce optical structures such as ridge waveguides or grooves for fiber coupling normally requires relatively slow processes such as ion milling. The authors have developed a laser-driven chemical etching process for etching highly unreactive ionic solids based on the fusion of salts in the molten phase and show that the etch rate can be more than 100 times faster than ion milling rates. This process involves spatially localized melting of LiNbO/sub 3/ by high-power density laser pulses with photon energies in excess of the band gap of LiNbO/sub 3/. While molten, LiNbO/sub 3/ undergoes reaction with a surface coating of KF to form niobium oxyfluoride anions by fusion of the salts. The resulting solid is highly water soluble. The insolubility of LiNbO/sub 3/ permits subsequent removal of only the irradiated area by rinsing in water. Surface morphology is determined by laser power density. The process exhibits a wavelength dependence

Some problems of neutron source multiplication method for site measurement technology in nuclear critical safety

International Nuclear Information System (INIS)

Shi Yongqian; Zhu Qingfu; Hu Dingsheng; He Tao; Yao Shigui; Lin Shenghuo

2004-01-01

The paper gives experiment theory and experiment method of neutron source multiplication method for site measurement technology in the nuclear critical safety. The measured parameter by source multiplication method actually is a sub-critical with source neutron effective multiplication factor k s , but not the neutron effective multiplication factor k eff . The experiment research has been done on the uranium solution nuclear critical safety experiment assembly. The k s of different sub-criticality is measured by neutron source multiplication experiment method, and k eff of different sub-criticality, the reactivity coefficient of unit solution level, is first measured by period method, and then multiplied by difference of critical solution level and sub-critical solution level and obtained the reactivity of sub-critical solution level. The k eff finally can be extracted from reactivity formula. The effect on the nuclear critical safety and different between k eff and k s are discussed

LaNiO{sub 3} buffer layers for high critical current density YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} and Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8{minus}{delta}} films

Energy Technology Data Exchange (ETDEWEB)

Carlson, C.M.; Parilla, P.A.; Siegal, M.P.; Ginley, D.S.; Wang, Y.; Blaugher, R.D.; Price, J.C.; Overmyer, D.L.; Venturini, E.L.

1999-10-01

We demonstrate high critical current density superconducting films of YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} (YBCO) and Tl{sub 2}Ba{sub 2}CaCu{sub 2}O{sub 8{minus}{delta}} (Tl-2212) using LaNiO{sub 3} (LNO) buffer layers. YBCO films grown on an LNO buffer layer have only a slightly lower J{sub c} (5 K, H=0) than films grown directly on a bare LaAlO{sub 3} substrate. YBCO films grown on LNO buffer layers exhibit minor microstructural disorder and enhanced flux pinning. LNO-buffered Tl-2212 samples show large reductions in J{sub c} at all temperatures and fields compared to those grown on bare LaAlO{sub 3}, correlating to both {ital a}-axis grain and nonsuperconducting phase formation. LNO could be a promising buffer layer for both YBCO and Tl-based superconducting films in coated conductor applications. {copyright} {ital 1999 American Institute of Physics.}

Critical experiment study on uranyl nitrate solution experiment facility

International Nuclear Information System (INIS)

Zhu Qingfu; Shi Yongqian; Wang Jinrong

2005-01-01

The Uranyl Nitrate Solution Experiment Facility was constructed for the research on nuclear criticality safety. In this paper, the configuration of the facility is introduced; a series of critical experiments on uranyl nitrate solution is described later, which were performed for various uranium concentrations under different conditions, i.e. with or without neutron absorbers in the core and with or without water-reflector outside the core. Critical volume and the minimum 235U critical mass for different uranium concentrations are presented. Finally, theoretical analysis is made on the experimental results. (authors)

Effect of uniaxial strain on the quantum critical phase of Sr{sub 3}Ru{sub 2}O{sub 7}

Energy Technology Data Exchange (ETDEWEB)

Barber, Mark E.; Brodsky, Daniel O.; Mackenzie, Andrew P. [Scottish Universities Physics Alliance (SUPA), School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS (United Kingdom); Max Planck Institute for Chemical Physics of Solids, Noethnitzer Strasse 40, Dresden 01187 (Germany); Hicks, Clifford W. [Max Planck Institute for Chemical Physics of Solids, Noethnitzer Strasse 40, Dresden 01187 (Germany); Perry, Robin [School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3FD (United Kingdom)

2016-07-01

Sr{sub 3}Ru{sub 2}O{sub 7} has a metamagnetic quantum critical endpoint, which in highly pure samples is masked by a novel phase. This phase is isotropic in the absence of symmetry-breaking fields, but weak in-plane magnetic fields are well-known to induce strong resistive anisotropy, leading to speculation that the phase intrinsically breaks the tetragonal symmetry of the lattice. We have used uniaxial strain to break the symmetry of the lattice and have found a dramatic response: compression by 0.1%, for example, induces a resistive anisotropy of ∝ 2.5. I will discuss these results in the context of the underlying symmetry of the anomalous phase.

Transmutation of uranium and thorium in the particle field of the Quinta sub-critical assembly

Science.gov (United States)

Hashemi-Nezhad, S. R.; Asquith, N. L.; Voronko, V. A.; Sotnikov, V. V.; Zhadan, Alina; Zhuk, I. V.; Potapenko, A.; Husak, Krystsina; Chilap, V.; Adam, J.; Baldin, A.; Berlev, A.; Furman, W.; Kadykov, M.; Khushvaktov, J.; Kudashkin, I.; Mar'in, I.; Paraipan, M.; Pronskih, V.; Solnyshkin, A.; Tyutyunnikov, S.

2018-03-01

The fission rates of natural uranium and thorium were measured in the particle field of Quinta, a 512 kg natural uranium target-blanket sub-critical assembly. The Quinta assembly was irradiated with deuterons of energy 4 GeV from the Nuclotron accelerator of the Joint Institute for Nuclear Research (JINR), Dubna, Russia. Fission rates of uranium and thorium were measured using Gamma spectroscopy and fission track techniques. The production rate of 239Np was also measured. The obtained experimental results were compared with Monte Carlo predictions using the MCNPX 2.7 code employing the physics and fission-evaporation models of INCL4-ABLA, CEM03.03 and LAQGSM03.03. Some of the neutronic characteristics of the Quinta are compared with the "Energy plus Transmutation (EpT)" subcritical assembly, which is composed of a lead target and natU blanket. This comparison clearly demonstrates the importance of target material, neutron moderator and reflector types on the performance of a spallation neutron driven subcritical system. As the dimensions of the Quinta are very close to those of an optimal multi-rod-uranium target, the experimental and Monte Carlo calculation results presented in this paper provide insights on the particle field within a uranium target as well as in Accelerator Driven Systems in general.

Hypoeutectic melting in the UO{sub 2-x}-Gd{sub 2}O{sub 3} system

Energy Technology Data Exchange (ETDEWEB)

Journeau, Christophe, E-mail: christophe.journeau@cea.fr [CEA, DEN, SMTA, LPMA, Cadarache, F13108 St Paul lez Durance (France); Fouquart, Pascal [CEA, DEN, SMTA, LPMA, Cadarache, F13108 St Paul lez Durance (France); Domenger, Renaud; Allegri, Patrick [CEA, DEN, SGCS, LMAC, Marcoule, F30207 Bagnols sur Cèze (France)

2017-05-15

Gadolinium is one of the best neutron absorber materials and its use can be considered as a sacrificial material in a Sodium Fast Reactor core catcher in view of preventing recriticallity. A series of experiments have been conducted in the VITI induction-heated facility to study the melting in the UO{sub 2-x}-Gd{sub 2}O{sub 3} system with 60–87 mol% gadolinia. These experiments have indicated that the eutectic composition is around 92 mol% Gd{sub 2}O{sub 3} – 8 mol% UO{sub 2-x} and that the liquidus line is close to that of Popov et al. [Atom. Energ. 110 (2011) pp. 221–229] phase diagram. - Highlights: •Melting/Solidification experiments with UO{sub 2-x} and Gd{sub 2}O{sub 3} in reducing environment. •Eutectic composition around 92 mol% Gd{sub 2}O{sub 3}-8 mol% UO{sub 2-x}. •UO{sub 2-x} - Gd{sub 2}O{sub 3} liquidus line seems close to that of the pseudobinary phase diagram proposed by Popov et al. •Results will support the assessment of Gd{sub 2}O{sub 3} as a sacrificial material to mitigate criticality risk in SFR core catchers.

Fabrication and high visible-light-driven photocurrent response of g-C{sub 3}N{sub 4} film: The role of thiourea

Energy Technology Data Exchange (ETDEWEB)

Ye, Lijuan; Chen, Shijian, E-mail: sjchen@cqu.edu.cn

2016-12-15

Highlights: • Thiourea promotes the growth and crystalline of the g-C{sub 3}N{sub 4} films on ITO. • Thiourea introduces S dopants into the g-C{sub 3}N{sub 4} films. • The obtained S-doped g-C{sub 3}N{sub 4} thin films show high VLD photocurrent response. • Three heterojunction structure types based on the g-C{sub 3}N{sub 4} films are proposed. - Abstract: We report on a convenient CVD fabrication of the uniform, compact and reproducible g-C{sub 3}N{sub 4} solid films on indium-tin oxide substrates. It is found that mixing quantitative thiourea into melamine as co-precursor prompts the deposition of greenish-yellow, transparent and smooth g-C{sub 3}N{sub 4} thin films. The thiourea apparently affects the crystalline, the surface morphologies and the energy band structures of g-C{sub 3}N{sub 4} films by modulating the polymerization process of the precursors, and simultaneously introduces S dopants into the g-C{sub 3}N{sub 4} films. Due to these roles of thiourea, the obtained S-doped g-C{sub 3}N{sub 4} films as a photoelectrode show a high and stable visible-light-driven photocurrent response. To further improve the photocurrent, the construction of three heterojunction structure types based on g-C{sub 3}N{sub 4} films is proposed and the corresponding charge transfer mechanisms are well discussed. The successful fabrication of high quality g-C{sub 3}N{sub 4} films in this work provides a footstone to construct the heterojunction film structures based on the carbon nitrides for the photoelectrochemical overall water splitting.

Generation of integral experiment covariance data and their impact on criticality safety validation

Energy Technology Data Exchange (ETDEWEB)

Stuke, Maik; Peters, Elisabeth; Sommer, Fabian

2016-11-15

The quantification of statistical dependencies in data of critical experiments and how to account for them properly in validation procedures has been discussed in the literature by various groups. However, these subjects are still an active topic in the Expert Group on Uncertainty Analysis for Criticality Safety Assessment (UACSA) of the OECDNEA Nuclear Science Committee. The latter compiles and publishes the freely available experimental data collection, the International Handbook of Evaluated Criticality Safety Benchmark Experiments, ICSBEP. Most of the experiments were performed as series and share parts of experimental setups, consequently leading to correlation effects in the results. The correct consideration of correlated data seems to be inevitable if the experimental data in a validation procedure is limited or one cannot rely on a sufficient number of uncorrelated data sets, e.g. from different laboratories using different setups. The general determination of correlations and the underlying covariance data as well as the consideration of them in a validation procedure is the focus of the following work. We discuss and demonstrate possible effects on calculated k{sub eff}'s, their uncertainties, and the corresponding covariance matrices due to interpretation of evaluated experimental data and its translation into calculation models. The work shows effects of various modeling approaches, varying distribution functions of parameters and compares and discusses results from the applied Monte-Carlo sampling method with available data on correlations. Our findings indicate that for the reliable determination of integral experimental covariance matrices or the correlation coefficients a detailed study of the underlying experimental data, the modeling approach and assumptions made, and the resulting sensitivity analysis seems to be inevitable. Further, a Bayesian method is discussed to include integral experimental covariance data when estimating an

IAEA coordinated research project (CRP) on 'Analytical and experimental benchmark analyses of accelerator driven systems'

Energy Technology Data Exchange (ETDEWEB)

Abanades, Alberto [Universidad Politecnica de Madrid (Spain); Aliberti, Gerardo; Gohar, Yousry; Talamo, Alberto [ANL, Argonne (United States); Bornos, Victor; Kiyavitskaya, Anna [Joint Institute of Power Eng. and Nucl. Research ' Sosny' , Minsk (Belarus); Carta, Mario [ENEA, Casaccia (Italy); Janczyszyn, Jerzy [AGH-University of Science and Technology, Krakow (Poland); Maiorino, Jose [IPEN, Sao Paulo (Brazil); Pyeon, Cheolho [Kyoto University (Japan); Stanculescu, Alexander [IAEA, Vienna (Austria); Titarenko, Yury [ITEP, Moscow (Russian Federation); Westmeier, Wolfram [Wolfram Westmeier GmbH, Ebsdorfergrund (Germany)

2008-07-01

In December 2005, the International Atomic Energy Agency (IAEA) has started a Coordinated Research Project (CRP) on 'Analytical and Experimental Benchmark Analyses of Accelerator Driven Systems'. The overall objective of the CRP, performed within the framework of the Technical Working Group on Fast Reactors (TWGFR) of IAEA's Nuclear Energy Department, is to increase the capability of interested Member States in developing and applying advanced reactor technologies in the area of long-lived radioactive waste utilization and transmutation. The specific objective of the CRP is to improve the present understanding of the coupling of an external neutron source (e.g. spallation source) with a multiplicative sub-critical core. The participants are performing computational and experimental benchmark analyses using integrated calculation schemes and simulation methods. The CRP aims at integrating some of the planned experimental demonstration projects of the coupling between a sub-critical core and an external neutron source (e.g. YALINA Booster in Belarus, and Kyoto University's Critical Assembly (KUCA)). The objective of these experimental programs is to validate computational methods, obtain high energy nuclear data, characterize the performance of sub-critical assemblies driven by external sources, and to develop and improve techniques for sub-criticality monitoring. The paper summarizes preliminary results obtained to-date for some of the CRP benchmarks. (authors)

Benchmarks of subcriticality in accelerator-driven system at Kyoto University Critical Assembly

Directory of Open Access Journals (Sweden)

Cheol Ho Pyeon

2017-09-01

Full Text Available Basic research on the accelerator-driven system is conducted by combining 235U-fueled and 232Th-loaded cores in the Kyoto University Critical Assembly with the pulsed neutron generator (14 MeV neutrons and the proton beam accelerator (100 MeV protons with a heavy metal target. The results of experimental subcriticality are presented with a wide range of subcriticality level between near critical and 10,000 pcm, as obtained by the pulsed neutron source method, the Feynman-α method, and the neutron source multiplication method.

Construction of STACY (Static Experiment Critical Facility)

International Nuclear Information System (INIS)

Murakami, Kiyonobu; Onodera, Seiji; Hirose, Hideyuki

1998-08-01

Two critical assemblies, STACY (Static Experiment Critical Facility) and TRACY (Transient Experiment Critical Facility), were constructed in NUCEF (Nuclear Fuel Cycle Safety Engineering Research Facility) to promote researches on the criticality safety at a reprocessing facility. STACY aims at providing critical data of uranium nitrate solution, plutonium nitrate solution and their mixture while varying concentration of solution fuel, core tank shape and size and neutron reflecting condition. STACY achieved first criticality in February 1995, and passed the licensing inspection by STA (Science and Technology Agency of Japan) in May. After that a series of critical experiments commenced with 10 w/o enriched uranium solution. This report describes the outline of STACY at the end of FY 1996. (author)

Monte Carlo analysis of the slightly enriched uranium-D2O critical experiment LTRIIA (AWBA Development Program)

International Nuclear Information System (INIS)

Hardy, J. Jr.; Shore, J.M.

1981-11-01

The Savannah River Laboratory LTRIIA slightly-enriched uranium-D 2 O critical experiment was analyzed with ENDF/B-IV data and the RCP01 Monte Carlo program, which modeled the entire assembly in explicit detail. The integral parameters delta 25 and delta 28 showed good agreement with experiment. However, calculated K/sub eff/ was 2 to 3% low, due primarily to an overprediction of U238 capture. This is consistent with results obtained in similar analyses of the H 2 O-moderated TRX critical experiments. In comparisons with the VIM and MCNP2 Monte Carlo programs, good agreement was observed for calculated reeaction rates in the B 2 =0 cell

CM-244 as multiplier and breeder in a ThO/sub 2/ hybrid blanket driven by a (D,T) source

International Nuclear Information System (INIS)

Sahin, S.; Al-Kusayer, T.A.

1986-01-01

The safeguard aspects of Cm-244 - a nuclear waste product in LWRs - in a cylindrical hybrid blanket, driven by a (D,T) fusion neutron source have been analyzed. Cm-244 is investigated for two different applications: 1) as a neutron multiplier between the first wall and the fuel zone in a blanket with ThO/sub 2/; and 2) as a component of the mixed fuel, ThO/sub 2/-Cm/sup 244/O/sub 2/, used for power flattening in a hybrid blanket. The calculations show that a relatively small driven with 100 MW/sub th/ fusion power could produce about 5 kg/year Cm-245, enough to provide nuclear fuel for up to 50 explosives. The study suggests an extension of the safe-guarding regulations prior to the commercial introduction of fusion reactors in the energy market

A Critical Review of the Impacts of Leaking CO<sub>2sub> Gas and Brine on Groundwater Quality

Energy Technology Data Exchange (ETDEWEB)

Qafoku, Nikolla [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Zheng, Liange [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Bacon, Diana H. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Lawter, Amanda R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Brown, Christopher F. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

2015-09-30

Geological carbon sequestration (GCS) is a global carbon emission reduction strategy involving the capture of CO<sub>2sub> emitted from fossil fuel burning power plants, as well as the subsequent injection of the captured CO<sub>2sub> gas into deep saline aquifers or depleted oil and gas reservoirs. A critical question that arises from the proposed GCS is the potential impacts of CO<sub>2sub> injection on the quality of drinking-water systems overlying CO<sub>2sub> sequestration storage sites. Although storage reservoirs are evaluated and selected based on their ability to safely and securely store emplaced fluids, leakage of CO<sub>2sub> from storage reservoirs is a primary risk factor and potential barrier to the widespread acceptance of geologic CO<sub>2sub> sequestration (OR Harvey et al. 2013; Y-S Jun et al. 2013; DOE 2007). Therefore, a systematic understanding of how CO<sub>2sub> leakage would affect the geochemistry of potable aquifers, and subsequently control or affect elemental and contaminant release via sequential and/or simultaneous abiotic and biotic processes and reactions is vital.

The Zeus Copper/Uranium Critical Experiment at NCERC

International Nuclear Information System (INIS)

Sanchez, Rene G.; Hayes, David K.; Bounds, John Alan; Jackman, Kevin R.; Goda, Joetta M.

2012-01-01

A critical experiment was performed to provide nuclear data in a non-thermal neutron spectrum and to reestablish experimental capability relevant to Stockpile Stewardship and Technical Nuclear Forensic programs. Irradiation foils were placed at specific locations in the Zeus all oralloy critical experiment to obtain fission ratios. These ratios were compared with others from other critical assemblies to assess the degree of softness in the neutron spectrum. This critical experiment was performed at the National Criticality Experiments Research Center (NCERC) in Nevada.

Evaluation of Model Driven Development of Safety Critical Software in the Nuclear Power Plant I and C system

International Nuclear Information System (INIS)

Jung, Jae Cheon; Chang, Hoon Seon; Chang, Young Woo; Kim, Jae Hack; Sohn, Se Do

2005-01-01

The major issues of the safety critical software are formalism and V and V. Implementing these two characteristics in the safety critical software will greatly enhance the quality of software product. The structure based development requires lots of output documents from the requirements phase to the testing phase. The requirements analysis phase is open omitted. According to the Standish group report in 2001, 49% of software project is cancelled before completion or never implemented. In addition, 23% is completed and become operational, but over-budget, over the time estimation, and with fewer features and functions than initially specified. They identified ten success factors. Among them, firm basic requirements and formal methods are technically achievable factors while the remaining eight are management related. Misunderstanding of requirements due to lack of communication between the design engineer and verification engineer causes unexpected result such as functionality error of system. Safety critical software shall comply with such characteristics as; modularity, simplicity, minimizing the sub-routine, and excluding the interrupt routine. In addition, the crosslink fault and erroneous function shall be eliminated. The easiness of repairing work after the installation shall be achieved as well. In consideration of the above issues, we evaluate the model driven development (MDD) methods for nuclear I and C systems software. For qualitative analysis, the unified modeling language (UML), functional block language (FBL) and the safety critical application environment (SCADE) are tested for the above characteristics

Critical condition for current-driven instability excited in turbulent heating of TRIAM-1 tokamak plasma

Energy Technology Data Exchange (ETDEWEB)

Nakamura, Y; Watanabe, T; Nagao, A; Nakamura, K; Kikuchi, M; Aoki, T; Hiraki, N; Itoh, S [Kyushu Univ., Fukuoka (Japan). Research Inst. for Applied Mechanics; Mitarai, O

1982-02-01

Critical condition for current-driven instability excited in turbulently heated TRIAM-1 tokamak plasma is investigated experimentally. Resistive hump in loop voltage, plasma density fluctuation and rapid increase of electron temperature in a skin layer are simultaneously observed at the time when the electron drift velocity amounts to the critical drift velocity for low-frequency ion acoustic instability.

Measurements of the critical parameters for {l_brace}xNH{sub 3} + (1 - x)H{sub 2}O{r_brace} with x = (0.9098, 0.7757, 0.6808)

Energy Technology Data Exchange (ETDEWEB)

Sakabe, A.; Arai, D. [Centre for Multiscale Mechanics and Mechanical Systems, Keio University, Yokohama 223-8522 (Japan); Miyamoto, H. [Department of Mechanical Systems Engineering, Toyama Prefectural University, Imizu 939-0398 (Japan)], E-mail: miyamoto@pu-toyama.ac.jp; Uematsu, M. [Centre for Multiscale Mechanics and Mechanical Systems, Keio University, Yokohama 223-8522 (Japan)

2008-10-15

Measurements of the critical parameters for {l_brace}xNH{sub 3} + (1 - x)H{sub 2}O{r_brace} with x = (0.9098, 0.7757, 0.6808) were carried out by using a metal-bellows variable volumometer with an optical cell. The expanded uncertainties (k = 2) in temperature, pressure, density, and composition measurements have been estimated to be less than 3.2 mK, 3.2 kPa, 0.3 kg . m{sup -3}, and 8.8 . 10{sup -4}, respectively. In each mole fraction, the critical temperature T{sub c} was first determined on the basis of the intensity of the critical opalescence. The critical pressure p{sub c} and critical density {rho}{sub c} were then determined as the point at which the meniscus disappears on the isotherm at T = T{sub c}. The expanded uncertainties (k = 2) in the present critical parameters have also been estimated. Comparisons of the present values with the literature data as well as the calculated values afforded using the equation of state are also presented.

Chasing {theta}{sub 13} with new reactor neutrino experiments

Energy Technology Data Exchange (ETDEWEB)

Lasserre, Th. [DSM/DAPNIA/SPP, CEA/Saclay, 91191 Gif-sur-Yvette (France)

2005-12-15

It is now widely accepted that a new middle baseline disappearance reactor neutrino experiment with multiple detectors could provide a clean measurement of the {theta}{sub 13} mixing angle, free from any parameter degeneracies and correlations induced by matter effect and the unknown leptonic Dirac CP phase. The current best constraint on the third mixing angle comes from the Chooz reactor neutrino experiment sin{sup 2}(2{theta}{sub 13})<0.2 (90 % C.L., {delta}m{sub atm}{sup 2}=2.010{sup -3} eV{sup 2}). Several projects of experiment, with different timescales, have been proposed over the last two years all around the world. Their sensitivities range from sin{sup 2}(2{theta}{sub 13})<0.01 to 0.03, having thus an excellent discovery potential of the {nu}{sub e} fraction of {nu}{sub 3}.

The effect of heterogeneity on the character of density-driven natural convection of CO{sub 2} overlying a brine layer

Energy Technology Data Exchange (ETDEWEB)

Farajzadeh, R. [Shell International Exploration and Production, Houston, TX (United States); Ranganathan, P.; Zitha, P.L.J.; Bruining, J. [Delft Univ. of Technology, Delft (Netherlands)

2010-07-01

This paper investigated the effect of heterogeneity on the character of natural-convection flow of carbon dioxide (CO{sub 2}) in aquifers and on the dissolution rate of CO{sub 2} in brine, contributing to a better understanding of the effect of heterogeneity on CO{sub 2} mass transfer in aquifers, which is necessary for efficient storage of CO{sub 2} in aquifers. The aquifer permeability, which is in practice heterogeneous, largely governs the efficiency of mixing in density-driven natural convection. The aquifer's degree of permeability variance and the correlation length informs the character of flow-driven mixing processes. Numerical simulation was used to identify different flow regimes of a density-driven natural flow regime. Heterogeneous fields were generated using a spectral method that allows the use of power-law variograms. From the simulations it was observed that the rate of mass transfer of carbon dioxide (CO{sub 2}) into water is higher for heterogeneous media. The formulation of the physical model and related equations and the method for generating the permeability fields were described. The simulation results indicated that gravity-induced fingering is the dominant pattern in low heterogeneity, but fingering will not occur in realistic porous media. The results also showed that the permeability field structure dominates at moderate heterogeneity, and that the flow is dispersive at high heterogeneity when the correlation length of the field is small. Heterogeneous media facilitate a larger rate of CO{sub 2} dissolution than homogenous media, which means that the former can store larger volumes of CO{sub 2}. 49 refs., 3 tabs., 13 figs.

An ultrasonic therapeutic transducers using lead-free Na{sub 0.5}K{sub 0.5}NbO{sub 3}-CuNb{sub 2}O{sub 6} ceramics

Energy Technology Data Exchange (ETDEWEB)

Yang, Ming-Ru [Department of Electrical Engineering, National Cheng Kung University, Taiwan (China); Chu, Sheng-Yuan, E-mail: chusy@mail.ncku.edu.t [Department of Electrical Engineering, National Cheng Kung University, Taiwan (China); Advanced Optoelectronic Technology Center, National Cheng Kung University, Tainan 701, Taiwan (China); Institute of Nanotechnology and Microsystems Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Tsai, Cheng-Che [Department of Electronics Engineering and Computer Science, Tung-Fang Institute of Technology, Kaohsiung 829, Taiwan (China)

2010-10-08

Research highlights: {yields} In this paper, CN was added to NKN ceramics to decrease the sintering temperature and to improve the density and piezoelectric characteristics. The influence of CuNb{sub 2}O{sub 6} (CN) content on the microstructure, electrical properties, temperature stability, and mechanical properties of the synthesized samples was investigated. Results show that the samples synthesized with CN-doped not only improved the density but also exhibited superior piezoelectric characteristic, temperature stability of resonance frequency (TCF), and elastic stiffness coefficient than those of pure NKN piezoelectric ceramics. {yields} The bulk density (4.47 g/cm{sup 3}), k{sub p} (40%), k{sub t} (45%), Q{sub m} (1642), C{sub 33}{sup D} (19.64 x 10{sup 10} N/m{sup 2}), TCF (-0.011%/{sup o}C) and TCC (0.135%/{sup o}C) values for NKN-01CN ceramics obtained from experiments show excellent 'hard' piezoelectric properties. Furthermore, a lead-free NKN-01CN ultrasonic therapeutic transducer was successfully driven by a self-tuning circuit. - Abstract: In this work, we reports on the CuNb{sub 2}O{sub 6} (CN) modified lead-free Na{sub 0.5}K{sub 0.5}NbO{sub 3} (NKN) based piezoelectric ceramics were synthesized by solid-state reaction methods and sintered at 1075 {sup o}C for 3 h. A secondary phase of K{sub 4}CuNb{sub 8}O{sub 23} was found in the XRD pattern of NKN-based ceramics as the CN dopants is 1 mol%. Microstructural analyses of un-doped and CN-doped ceramics were performed in a scanning electron microscope. The influence of CN content on the microstructure, electrical properties, temperature stability, and mechanical properties of the synthesized ceramics was investigated. The results show that the synthesized ceramics with CN-doped not only had improved density but also exhibited superior piezoelectric characteristics, temperature stability of resonance frequency (TCF), and a better elastic stiffness coefficient than those of pure NKN piezoelectric

Benchmarking criticality safety calculations with subcritical experiments

International Nuclear Information System (INIS)

Mihalczo, J.T.

1984-06-01

Calculation of the neutron multiplication factor at delayed criticality may be necessary for benchmarking calculations but it may not be sufficient. The use of subcritical experiments to benchmark criticality safety calculations could result in substantial savings in fuel material costs for experiments. In some cases subcritical configurations could be used to benchmark calculations where sufficient fuel to achieve delayed criticality is not available. By performing a variety of measurements with subcritical configurations, much detailed information can be obtained which can be compared directly with calculations. This paper discusses several measurements that can be performed with subcritical assemblies and presents examples that include comparisons between calculation and experiment where possible. Where not, examples from critical experiments have been used but the measurement methods could also be used for subcritical experiments

The OPERA experiment. ν{sub μ}→ν{sub τ} oscillation discovered in appearance mode

Energy Technology Data Exchange (ETDEWEB)

Buettner, Benjamin [Universitaet Hamburg, Institut fuer Experimentalphysik (Germany); Collaboration: OPERA-Hamburg-Collaboration

2016-07-01

The primary goal of the OPERA long-baseline neutrino oscillation experiment is the first direct detection of ν{sub μ}→ν{sub τ} oscillations. The hybrid OPERA detector consists of a large-mass target made from lead and photo emulsions - providing micrometric resolution - and electronic detector parts for online readout. It is located in the LNGS underground laboratory, at a distance of 730 km from the SPS at CERN, where the CNGS ν{sub μ} beam is produced. The measurement of ν{sub τ} appearance relies on the detection of the decay of τ leptons which are created in ν{sub τ} charged current reactions. Data acquisition lasted from 2008 to 2012. With the collected data the OPERA experiment discovered ν{sub τ} appearance in the CNGS neutrino beam with a significance of 5.1 σ. This poster will give an overview about the OPERA experiment and the discovery of τ neutrino appearance in the CNGS neutrino beam.

Enhancement of critical current density of in situ processed MgB sub 2 tapes by WB addition

CERN Document Server

Fujii, H; Kumakura, H

2003-01-01

The effect of tungsten boride (WB) addition on the microstructure and superconducting properties of Fe-sheathed MgB sub 2 tapes has been investigated. The microstructure was not influenced appreciably by the addition, whereas the superconducting properties changed. Even by a 5 mol% addition, the critical temperature (T sub c) decreased by about 0.5 K. However, the field dependence of the inductive critical current density (J sub c sub i) became smaller with the increase in the amount of addition, suggesting that pinning centres effective in a high-field region were possibly introduced. The transport critical current density (J sub c sub t) at 4.2 K increased about twice by the 5 mol% addition and reached 15 and 5 kA cm sup - sup 2 at 8 and 10 T, respectively.

Design-theoretical study of cascade CO2 sub-critical mechanical compression/butane ejector cooling cycle

KAUST Repository

Petrenko, V.O.

2011-11-01

In this paper an innovative micro-trigeneration system composed of a cogeneration system and a cascade refrigeration cycle is proposed. The cogeneration system is a combined heat and power system for electricity generation and heat production. The cascade refrigeration cycle is the combination of a CO2 mechanical compression refrigerating machine (MCRM), powered by generated electricity, and an ejector cooling machine (ECM), driven by waste heat and using refrigerant R600. Effect of the cycle operating conditions on ejector and ejector cycle performances is studied. Optimal geometry of the ejector and performance characteristics of ECM are determined at wide range of the operating conditions. The paper also describes a theoretical analysis of the CO2 sub-critical cycle and shows the effect of the MCRM evaporating temperature on the cascade system performance. The obtained data provide necessary information to design a small-scale cascade system with cooling capacity of 10 kW for application in micro-trigeneration systems. © 2010 Elsevier Ltd and IIR. All rights reserved.

Conductivity fluctuation and superconducting parameters of the YBa{sub 2}Cu{sub 3-} {sub x} (PO{sub 4}) {sub x} O{sub 7-} {sub {delta}} material

Energy Technology Data Exchange (ETDEWEB)

Rojas Sarmiento, M.P. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, AA 14490, Bogota DC (Colombia); Uribe Laverde, M.A. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, AA 14490, Bogota DC (Colombia); Vera Lopez, E. [Grupo de Superficies, Electroquimica y Corrosion, UPTC, Tunja (Colombia); Landinez Tellez, D.A. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, AA 14490, Bogota DC (Colombia); Roa-Rojas, J. [Grupo de Fisica de Nuevos Materiales, Departamento de Fisica, Universidad Nacional de Colombia, AA 14490, Bogota DC (Colombia)]. E-mail: jroar@unal.edu.co

2007-09-01

Synthesis of the YBa{sub 2}Cu{sub 3-} {sub x} (PO{sub 4}) {sub x} O{sub 7-} {sub {delta}} superconducting material by the standard solid-state reaction is reported. DC resistivity measurements reveal the improvement of the critical temperature (T {sub C}) when substitution of phosphate in the Cu sites is performed. A bulk T {sub C}=97 K was determined by the criterion of the maximum in the temperature derivative of electrical resistivity. Structure characterization by means the X-ray diffraction technique shows the crystalline appropriated distribution of PO{sub 4} into the CuO{sub 2} superconducting planes. In order to examine the effect of phosphates on the pairing mechanism close to T {sub C}, conductivity fluctuation analysis was performed by the method of logarithmic temperature derivative of the conductivity excess. We found the occurrence of Gaussian-like fluctuations. The correlations of the critical exponents with the dimensionality of the fluctuation system for each Gaussian regime were performed by using the Aslamazov-Larkin theory. The Ginzburg number for this superconducting material is predicted and the critical magnetic fields, critical current density and the jump in the specific heat at the critical temperature are theoretically determined.

Construction of new critical experiment facilities in JAERI

International Nuclear Information System (INIS)

Takeshita, Isao; Itahashi, Takayuki; Ogawa, Kazuhiko; Tonoike, Kotaro; Matsumura, Tatsuro; Miyoshi, Yoshinori; Nakajima, Ken; Izawa, Naoki

1995-01-01

Japan Atomic Energy Research Institute (JAERI) has promoted the experiment research program on criticality safety since early in 1980s and two types of new critical facilities, Static Experiment Critical Facility (STACY) and Transient Experiment Critical Facility (TRACY) were completed on 1994 in Nuclear Fuel Cycle Safety Engineering Research Facility (NUCEF) of JAERI Tokai Research Establishment. STACY was designed so as to obtain critical mass data of low enriched uranium and plutonium solution which is extensively handled in LWR fuel reprocessing plant. TRACY is the critical facility where critical accident phenomenon is demonstrated with low enriched uranium nitrate solution. For criticality safety experiments with both facilities, the Fuel Treatment System is attached to them, where composition and concentration of uranium and plutonium nitrate solutions are widely varied so as to obtain experiments data covering fuel solution conditions in reprocessing plant. Design performances of both critical facilities were confirmed through mock-up tests of important components and cold function tests. Hot function test has started since January of 1995 and some of the results on STACY are to be reported. (author)

Na{sub 2}V{sub 3}O{sub 7}: An unusual low-dimensional quantum magnet

Energy Technology Data Exchange (ETDEWEB)

Gavilano, J.L. [Laboratorium fuer Festkoerperphysik, ETHZ, CH-8093 Zurich (Switzerland)]. E-mail: gavilano@phys.ethz.ch; Felder, E. [Laboratorium fuer Festkoerperphysik, ETHZ, CH-8093 Zurich (Switzerland); Rau, D. [Laboratorium fuer Festkoerperphysik, ETHZ, CH-8093 Zurich (Switzerland); Ott, H.R. [Laboratorium fuer Festkoerperphysik, ETHZ, CH-8093 Zurich (Switzerland); Millet, P. [Centre d' Elaboration des Materiaux et d' Etudes Structurales, 29, rue J. Marvig, 31055 Toulouse Cedex (France); Mila, F. [Institute of Theoretical Physics, EPFL, CH - 1015 Lausanne (Switzerland); Cichorek, T. [Max-Planck-Institut fuer Chemische Physik fester Stoffe, 01187 Dresden (Germany); Mota, A.C. [Max-Planck-Institut fuer Chemische Physik fester Stoffe, 01187 Dresden (Germany)

2006-05-01

Results of present and previous measurements of the {sup 23}Na NMR response, dc- and ac-magnetic susceptibilities and the specific heat of Na{sub 2}V{sub 3}O{sub 7} at low temperatures suggest that this material is close to a quantum critical point (QCP) at {mu}{sub 0}H=0T. The experimental data can be explained by assuming that below 100K the localized V magnetic moments (S=12) form a collection of dimers, with a broad distribution of singlet-triplet gaps. Most of the dimers adopt a singlet ground state with gaps between 0 and 350K. A small fraction of them forms triplet ground states with gaps between 0 and 15K. The degeneracy of the triplet ground states is lifted by a phase transition at an unusually low temperature of 0.086K. Modest magnetic fields effectively quench this low-temperature state and the system is driven away from the QCP as the applied fields are enhanced to above 1T.

The Kondo contribution to the electrical resistivity in UCu sub 5 sub - sub x Ni sub x and the non-Fermi liquid behaviour of UCu sub 4 Ni

CERN Document Server

Torre, L D L; Ellerby, M; McEwen, K A

2003-01-01

We report on electrical resistivity measurements performed on polycrystalline samples of UCu sub 5 sub - sub x Ni sub x (x = 0.25, 1). In order to extract the Kondo contribution to the resistivity, the experiments were carried out over a wide temperature range (0.4-800 K). From the analysis of our results, we conclude that the Kondo temperature takes values of T sub K approx 240 K for x = 1 and T sub K approx 245 K for x = 0.25, and that for both Ni concentrations the dominant part of the remarkably high residual resistivity (rho(0) approx 400 mu OMEGA cm) corresponds to the Kondo contribution. These results are discussed in comparison with previous analysis of specific heat and magnetic susceptibility data that produced similar values of T sub K. We interpret our results in terms of disorder-driven non-Fermi liquid behaviour for UCu sub 4 Ni, as indicated by the anomalous temperature dependences of the electrical, thermal and magnetic properties previously observed in this compound.

Critical experiments of JMTRC MEU cores

International Nuclear Information System (INIS)

Nagaoka, Y.; Takeda, K.; Shimakawa, S.; Koike, S.; Oyamada, R.

1984-01-01

The JMTRC, the critical facility of the Japan Materials Testing Reactor (JMTR), went critical on August 29, 1983, with 14 medium enriched uranium (MEU, 45%) fuel elements. Experiments are now being carried out to measure the change in various reactor characteristics between the previous HEU core and the new MEU fueled core. This paper describes the results obtained thus far on critical mass, excess reactivity, control rod worths and flux distribution, including preliminary neutronics calculations for the experiments using the SRAC code. (author)

Compilation of criticality data involving thorium or 233U and light water moderation

Energy Technology Data Exchange (ETDEWEB)

Gore, B.F.

1978-07-01

The literature has been searched for criticality data for light water moderated systems which contain thorium or /sup 233/U, and data found are compiled herein. They are from critical experiments, extrapolations, and exponential experiments performed with homogeneous solutions and metal spheres of /sup 233/U; with lattices of fuel rods containing highly enriched /sup 235/UO/sub 2/ - ThO/sub 2/ and /sup 233/UO/sub 2/ - ThO/sub 2/; and with arrays of cyclinders of /sup 233/U solutions. The extent of existing criticality data has been compared with that necessary to implement a thorium-based fuel cycle. No experiments have been performed with any solutions containing thorium. Neither do data exist for homogeneous /sup 233/U systems with H/U < 34, except for solid metal systems. Arrays of solution cylinders up to 3 x 3 x 3 have been studied. Data for solutions containing fixed or soluble poisons are very limited. All critical lattices using /sup 233/UO/sub 2/ - ThO/sub 2/ fuels (LWBR program) were zoned radially, and in most cases axially also. Only lattice experiments using /sup 235/UO/sub 2/ - ThO/sub 2/ fuels have been performed using a single fuel rod type. Critical lattices of /sup 235/UO/sub 2/ - ThO/sub 2/ rods poisoned with boron have been measured, but only exponential experiments have been performed using boron-poisoned lattices of /sup 233/UO/sub 2/ - ThO/sub 2/ rods. No criticality data exist for denatured fuels (containing significant amounts of /sup 238/U) in either solution or lattice configurations.

Tuning of a non-Fermi-liquid state in CeNiGa{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Hauser, R.; Bauer, E.; Kottar, A.; Hilscher, G. [T.U. Wien (Austria). Inst. fuer Experimentalphys.; Galli, M. [Inst. Naz. di Fisica della Materia and Dipt. di Fisica A. Volta, Univ. di Pavia (Italy); Kaczorowski, D. [Inst. of Low Temperature and Structure Research, Polish Acadamy of Sciences, Wroclaw (Poland)

1998-01-01

The antiferromagnetic order in the Kondo lattice CeNiGa{sub 2} is found to vanish at a critical pressure P{sub cr}{approx}4 kbar. For pressures ranging from 4 to 9 kbar a non-Fermi-liquid state where {rho}-{rho}{sub 0}{proportional_to}T{sup 3/2} is observed. By further increasing pressure or external magnetic field this compound is driven towards Fermi-liquid behavior. (orig.) 12 refs.

Influence of two-stage annealing treatment on critical current of bronze-processed multifilamentary Nb/sub 3/Sn superconducting materials

International Nuclear Information System (INIS)

Ochiai, S.; Osamura, K.; Ryoji, M.

1987-01-01

The influence of changes of volume fraction of Nb/sub 3/Sn, grain size and upper critical magnetic field due to two-stage annealing treatment (low temperature annealing to form fine grains + high temperature annealing to raise upper critical magnetic field) on overall critical current and critical current density were studied at magnetic field of 3-15 T. When annealing temperature was low (773-923 K) and the volume fraction of Nb/sub 3/Sn was low in first stage annealing, second stage annealing could raise the overall critical current over the range of the applied magnetic field due to increase in upper critical magnetic field H/sub c2/ and volume fraction of Nb/sub 3/Sn accompanying with reduction in Sn concentration in the bronze matrix, which played a role to reduce residual strain in Nb/sub 3/Sn, leading to high H/sub c2/ although the loss in pinning force arose from the coarsening of the grains. When the annealing temperature was high (973 K) and the Nb/sub 3/Sn was formed until the Sn was consumed in the first stage, second stage annealing could not raise the critical current due to increase in grain size and no effective increase in H/sub c2/. The critical current density at low magnetic fields below several Teslas was reduced by the second stage annealing due to increase in grain size but that at high fields was raised due to increase in high H/sub c2/. The reverse two-stage annealing treatment (high temperature annealing in the first stage+low temperature annealing in the second stage) reduced the H/sub c2/ slightly with increasing second stage annealing temperature and time. The critical current density at low magnetic fields was determined mainly by the grain size and that at high fields was determined by the combination of the upper critical field and grain size

Laser-driven polarized sources of hydrogen and deuterium

International Nuclear Information System (INIS)

Young, L.; Holt, R.J.; Green, M.C.; Kowalczyk, R.S.

1988-01-01

A novel laser-driven polarized source of hydrogen and deuterium which operates on the principle of spin exchange optical pumping is described. The advantages of this method over conventional polarized sources for internal target experiments are presented. Technological difficulties which prevent ideal source operation are outlined along with proposed solutions. At present, the laser-driven polarized hydrogen source delivers 8 /times/ 10 16 atoms/s with a polarization (P/sub z/) of 24%. 9 refs., 2 figs

Russian nuclear criticality experiments. Status and prospects

International Nuclear Information System (INIS)

Gagarinski, A.Yu.

2003-01-01

After the nuclear criticality had been reached on a uranium-graphite assembly for the first time in the Soviet Union on December 25, 1946, by I.V. Kurchatov and his team (1), the critical conditions in a great variety of multiplying media have been realized only in the Kurchatov Institute for at least several thousand times. Even the first Russian critical experiments carried out by Igor Kurchatov confirmed the unique merits of zero-power reactors: the most practically convenient range of parameters of kinetic response for variation of critical conditions, as well as invariability, over a wide range of the most important functions of neutron flux to reactor power. Neutron physics experiments have become a necessary stage in creation and improvement of nuclear reactors. Most critical experiments were performed mainly as a necessary stage of reactor design in the 60ies and 70ies, which has been the reactor 'golden age', when most of the total of over thousand nuclear reactors of various type and destination have been created worldwide. Though the ways of conducting critical measurements were very diversified, there are two main types of experiments. The first is so-called mock-up or prototype experiments when an exact (to the extent possible) simulation of the core is constructed to minimize the error in forecasting the operating reactor characteristics. Such experiments, which often represent the quality control of the core manufacturing and adjustment of core parameters to the design requirements, were carried out in Russia on critical assemblies of several plants, in design institutions (OKBM, Nizhni Novgorod; Electrostal and others), as well as in research centers (RRC 'Kurchatov Institute', etc.). Their results, which prevail today in the criticality database, even taking into account the capabilities provided by present-day calculation codes, are not well suited for new applications. It is hard to expect that the error resulting from inevitable idealization of

Electrically Driven Thermal Management: Flight Validation, Experiment Development, Future Technologies

Science.gov (United States)

Didion, Jeffrey R.

2018-01-01

Electrically Driven Thermal Management is an active research and technology development initiative incorporating ISS technology flight demonstrations (STP-H5), development of Microgravity Science Glovebox (MSG) flight experiment, and laboratory-based investigations of electrically based thermal management techniques. The program targets integrated thermal management for future generations of RF electronics and power electronic devices. This presentation reviews four program elements: i.) results from the Electrohydrodynamic (EHD) Long Term Flight Demonstration launched in February 2017 ii.) development of the Electrically Driven Liquid Film Boiling Experiment iii.) two University based research efforts iv.) development of Oscillating Heat Pipe evaluation at Goddard Space Flight Center.

Advanced electrical current measurements of microdischarges: evidence of sub-critical pulses and ion currents in barrier discharge in air

Science.gov (United States)

Synek, Petr; Zemánek, Miroslav; Kudrle, Vít; Hoder, Tomáš

2018-04-01

Electrical current measurements in corona or barrier microdischarges are a challenge as they require both high temporal resolution and a large dynamic range of the current probe used. In this article, we apply a simple self-assembled current probe and compare it to commercial ones. An analysis in the time and frequency domain is carried out. Moreover, an improved methodology is presented, enabling both temporal resolution in sub-nanosecond times and current sensitivity in the order of tens of micro-amperes. Combining this methodology with a high-tech oscilloscope and self-developed software, a unique statistical analysis of currents in volume barrier discharge driven in atmospheric-pressure air is made for over 80 consecutive periods of a 15 kHz applied voltage. We reveal the presence of repetitive sub-critical current pulses and conclude that these can be identified with the discharging of surface charge microdomains. Moreover, extremely low, long-lasting microsecond currents were detected which are caused by ion flow, and are analysed in detail. The statistical behaviour presented gives deeper insight into the discharge physics of these usually undetectable current signals.

EVIDENCE FOR H{sub 2} FORMATION DRIVEN DUST GRAIN ALIGNMENT IN IC 63

Energy Technology Data Exchange (ETDEWEB)

Andersson, B-G; De Buizer, J.; Charcos-Llorens, M. [SOFIA Science Center, USRA, NASA Ames Research Center, M.S. N211-3 Moffett Field, CA 94035 (United States); Piirola, V. [Finnish Centre for Astronomy with ESO, University of Turku, Väisäläntie 20, FI-21500 Piikkiö (Finland); Clemens, D. P. [Institute for Astrophysical Research, Boston University, Boston, MA 02215 (United States); Uomoto, A. [Observatories of the Carnegie Institution, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Geballe, T. R. [Gemini Observatory, Northern Operations Center, 670 N. A' ohoku Place, Hilo, HI 96720 (United States); Lazarian, A.; Hoang, T. [Department of Astronomy, University of Wisconsin, 475 North Charter Street, Madison, WI 53706 (United States); Vornanen, T., E-mail: bg@sofia.usra.edu [Tuorla Observatory, University of Turku, Väisäläntie 20, FI-21500 Piikkiö (Finland)

2013-10-01

In the interstellar medium (ISM), molecular hydrogen is expected to form almost exclusively on the surfaces of dust grains. Due to that molecule's large formation energy (–4.5 eV), several dynamical effects are likely associated with the process, including the alignment of asymmetric dust grains with the ambient magnetic field. Such aligned dust grains are, in turn, believed to cause the broadband optical/infrared polarization observed in the ISM. Here, we present the first observational evidence for grain alignment driven by H{sub 2} formation, by showing that the polarization of the light from stars behind the reflection nebula IC 63 appears to correlate with the intensity of H{sub 2} fluorescence. While our results strongly suggest a role for 'Purcell rockets' in grain alignment, additional observations are needed to conclusively confirm their role. By showing a direct connection between H{sub 2} formation and a probe of the dust characteristics, these results also provide one of the first direct confirmations of the grain-surface formation of H{sub 2}. We compare our observations to ab initio modeling based on Radiative Torque Alignment (RAT) theory.

Critical Behavior of Thermal Expansion and Magnetostriction in the Vicinity of the First order transition at the Curie Point of Gd<sub>5sub>(Si_xGe>1-xsub>)>4sub>

Energy Technology Data Exchange (ETDEWEB)

Han, Mangui [Iowa State Univ., Ames, IA (United States)

2004-01-01

Thermal expansion (TE) and magnetostriction (MS) measurements have been conducted for Gd<sub>5sub>(Si_xGe>1-xsub>)>4sub> with a series of x values to study its critical behavior in the vicinity of transition temperatures. It was found that the Curie temperature of Gd<sub>5sub>(Si_xGe>1-xsub>)>4sub> for x 0 ~ 0.5 is dependent on magnetic field, direction of change of temperature (Tc on cooling was lower than Tc on heating), purity of Gd starting material, compositions, material preparation methods, and also can be triggered by the external magnetic field with a different dT/dB rate for different x values. For Gd<sub>5sub>(Si>1.95sub>Ge>2.05sub>), Gd<sub>5sub>(Si>2sub>Ge>2sub>), Gd<sub>5sub>(Si>2.09sub>Ge>1.91sub>), it was also found that the transition is a first order magneto-structural transition, which means the magnetic transition and crystalline structure transition occur simultaneously, and completely reversible. Temperature hysteresis and phase coexistence have been found to confirm that it is a first order transformation. While for Gd<sub>5sub>(Si>0.15sub>Ge>3.85sub>), it is partially reversible at some temperature range between the antiferromagnetic and the ferromagnetic state. For Gd<sub>5sub>(Si>2.3sub>Ge>1.7sub>) and Gd<sub>5sub>(Si>3sub>Ge>1sub>), it was a second order transformation between the paramagnetic and ferromagnetic state, because no ΔT have been found. Giant magnetostriction was only found on Gd<sub>5sub>(Si>1.95sub>Ge>2.05sub>), Gd<sub>5sub>(Si>2sub>Ge>2sub>), Gd<sub>5sub>(Si>2.09sub>Ge>1.91sub>) in their vicinity of first order transformation. MFM images have also been taken on polycrystal sample Gd<sub>5sub>(Si>2.09sub>Ge>1.91sub>) to investigate the transformation process. The results also indicates that the Curie temperature was lower and the thermally

Effect on C-axis transport properties of a critical state in Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8}

Energy Technology Data Exchange (ETDEWEB)

Cho, J.H.; Maley, M.P.; Bulaevskii, L.N.

1995-12-31

At low temperatures, the c-axis transport properties of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} single crystals depend strongly on the magnetic field history for fields applied along the c-axis, indicating the effect of a critical state in the ab direction. In this study, the authors report zero field cooled (ZFC), field cooled warming (FCW), and field cooled cooling (FCC) c-axis transport properties. In addition, they also report magnetic relaxation measurements on the same samples to identify the c-axis dissipation mechanism. They observe a relaxation of the c-axis resistivity that follows the relaxation of the flux profile across the ab plane. By identifying the irreversible temperature vs. magnetic field for H // c, they construct a phase diagram of vortex states. Finally, they will discuss the implication of the phase diagram and the features related to the transport properties of the Josephson-coupled system and the role of pancake vortices in highly two-dimensional superconductors.

Enhancement of localization phenomena driven by covalency in the SrBiMn{sub 1.75}Ti{sub 0.25}O{sub 6} manganite

Energy Technology Data Exchange (ETDEWEB)

Asensio de Lucas, E.; Alvarez-Serrano, I. [Depto. Quimica Inorganica I, Facultad Ciencias Quimicas, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Cuello, G.J. [Institut Laue-Langevin, 6 rue Jules Horowitz, F-38042 Grenoble (France); Garcia-Hernandez, M. [Instituto de Ciencia de Materiales de Madrid, CSIC, E-28049 Cantoblanco, Madrid (Spain); Lopez, M.L., E-mail: marisal@quim.ucm.es [Depto. Quimica Inorganica I, Facultad Ciencias Quimicas, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Pico, C.; Veiga, M.L. [Depto. Quimica Inorganica I, Facultad Ciencias Quimicas, Universidad Complutense de Madrid, E-28040 Madrid (Spain)

2012-05-05

Graphical abstract: Enhancement of localization phenomena driven by covalency in the BiSrMn{sub 1.75}Ti{sub 0.25}O{sub 6} manganite. The CO/OO phenomena and magnetic clusters (Mn{sub 4}) stabilization at temperatures up to 520 K in BiSrMn{sub 1.75}Ti{sub 0.25}O{sub 6} are connected to a structural transition. The observed enhancement of electronic localization is interpreted considering covalent effects of Ti{sup 4+} and Bi{sup 3+} cations as the main driving force. Highlights: Black-Right-Pointing-Pointer The structural, electronic and magnetic behaviour of the new SrBiMn{sub 1.75}Ti{sub 0.25}O{sub 6} manganite is reported. Black-Right-Pointing-Pointer A structural transition above 520 K takes place, coinciding with relevant changes in the transport properties. Black-Right-Pointing-Pointer The electronic behavior is interpreted in terms of a remarkably high orbital and charge ordering temperature and cluster models. Black-Right-Pointing-Pointer The observed features are explained considering a scenario in which bonds covalence is enhanced by the Bi{sup 3+} and Ti{sup 4+} cations. - Abstract: Manganites are materials that show remarkable phenomena related to charge orbital ordering (CO/OO) and it is extremely important to understand the fundamental nature of this behaviour. This paper reports on the structural, electronic and magnetic behaviour of the new SrBiMn{sub 1.75}Ti{sub 0.25}O{sub 6} manganite and the dependence of these properties with temperature. A detailed structural analysis has been carried out by electron, X-ray, neutron diffraction between 4 and 700 K. The electron diffraction patterns obtained at room temperature (RT) evidence that the average structure (a{approx}b{approx}{radical}(2)a{sub p} and c {approx} 2a{sub p}) presents a modulation that doubles the a and c lattice parameters. A very high charge ordering (CO) transition temperature of 510 K, similar to that found for the non-doped material, SrBiMn{sub 2}O{sub 6}, is observed. Above this

Microstructural and magneto-transport properties of Bi{sub 1.6}Pb{sub 0.4}Sr{sub 2}Ca{sub 1−x}Gd{sub x}Cu{sub 2}O{sub 8+δ} superconducting ceramics

Energy Technology Data Exchange (ETDEWEB)

Boudjadja, Y., E-mail: yazid.bouj@Gmail.com [NDT Laboratory, Faculty of Science and Technology, Jijel University, Jijel 18000 (Algeria); Amira, A.; Mahamdioua, N.; Saoudel, A. [NDT Laboratory, Faculty of Science and Technology, Jijel University, Jijel 18000 (Algeria); Menassel, S. [MSAR Unit, Physics Department, Constantine 1 University, Constantine 25017 (Algeria); Varilci, A.; Terzioglu, C.; Altintas, S.P. [Department of Physics, Faculty of Arts and Sciences, AIB University, Bolu 14280 (Turkey)

2017-01-15

This study aims to investigate the effect of Gd doping on the phase formation, microstructure, transport and magnetic properties of the Bi(Pb)-2212 system. A series of superconducting bulks with a nominal composition of Bi{sub 1.6}Pb{sub 0.4}Sr{sub 2}Ca{sub 1−x}Gd{sub x}Cu{sub 2}O{sub 8+δ} with x=0, 0.05, 0.10 and 0.15 are synthesized by the solid state synthesis route. The formed samples are characterized by means of X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), electrical transport and magnetic measurements. The experiment results reveal that all the samples doped are composed of Bi-2212 phase and traces of Bi-2201 secondary phase when compared to the undoped sample. The refinement of cell parameters shows that the doping reduces the cell volume of the samples. The texture degree decreases with doping while the degree of orthorhombicity increases. Quantitative EDS analysis confirms that Gd atoms are successfully introduced into crystalline structure. The SEM micrographs show randomly distributed grains with a flake-like shape. The highest value of onset critical transition temperatures is obtained for x=0.10 and is about 90.22 K, which correlates well with the observed slope of resistivity and the hole concentration of the CuO{sub 2} layers. Magnetic hysteresis loops suggest that the diamagnetism, remanant magnetization and lower critical field are better for x=0.10. Based on the enhancements of both grain boundary weak-links and flux pinning centers, improvement of the critical current densities and flux pinning density is obtained with this kind of doping.

Critical experiments facility and criticality safety programs at JAERI

International Nuclear Information System (INIS)

Kobayashi, Iwao; Tachimori, Shoichi; Takeshita, Isao; Suzaki, Takenori; Miyoshi, Yoshinori; Nomura, Yasushi

1985-10-01

The nuclear criticality safety is becoming a key point in Japan in the safety considerations for nuclear installations outside reactors such as spent fuel reprocessing facilities, plutonium fuel fabrication facilities, large scale hot alboratories, and so on. Especially a large scale spent fuel reprocessing facility is being designed and would be constructed in near future, therefore extensive experimental studies are needed for compilation of our own technical standards and also for verification of safety in a potential criticality accident to obtain public acceptance. Japan Atomic Energy Research Institute is proceeding a construction program of a new criticality safety experimental facility where criticality data can be obtained for such solution fuels as mainly handled in a reprocessing facility and also chemical process experiments can be performed to investigate abnormal phenomena, e.g. plutonium behavior in solvent extraction process by using pulsed colums. In FY 1985 detail design of the facility will be completed and licensing review by the government would start in FY 1986. Experiments would start in FY 1990. Research subjects and main specifications of the facility are described. (author)

Critical experiments with mixed oxide fuel

International Nuclear Information System (INIS)

Harris, D.R.

1997-01-01

This paper very briefly outlines technical considerations in performing critical experiments on weapons-grade plutonium mixed oxide fuel assemblies. The experiments proposed would use weapons-grade plutonium and Er 2 O 3 at various dissolved boron levels, and for specific fuel assemblies such as the ABBCE fuel assembly with five large water holes. Technical considerations described include the core, the measurements, safety, security, radiological matters, and licensing. It is concluded that the experiments are feasible at the Rensselaer Polytechnic Institute Reactor Critical Facility. 9 refs

Description of Supercritical CO{sub 2} Compressor Experiment Loop

Energy Technology Data Exchange (ETDEWEB)

Lee, Je Kyoung; Lee, Jeong Ik; Ahn, Yoonhan; Kim, Seong Gu [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Cha, Je Eun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2013-10-15

The full scope of SCIEL project is to demonstrate high efficiency with simple recuperated cycle layout or recompressing layout, which the final cycle layout will be determined by the obtained compressor performance data. As a part of SCIEL project, S-CO{sub 2} compressor experiment facility has been constructed in KAERI. In this paper, current status of S-CO{sub 2} compressor experiment loop will be reviewed. With the growing interest in developing an advanced nuclear power plant, power conversion cycle innovation has been the part of this effort to secure high economics and enhanced safety. One of the main activities of power conversion cycle innovation is the development of Supercritical CO{sub 2} Brayton cycle technology. S-CO{sub 2} Brayton cycle concept was suggested in 1960s but the development and realization of the technology has been delayed up to now. In Korea, KAIST, KAERI and POSTECH are conducting research and development of Korean S-CO{sub 2} Brayton cycle technology by erecting the Supercritical CO{sub 2} Integral Experiment Loop (SCIEL)

Sub-Critical Nuclear Reactor Based on FFAG-Accelerator

Energy Technology Data Exchange (ETDEWEB)

Lee, Hee Seok; Kang, Hung Sik; Lee, Tae Yeon [Pohang Accelerator Laboratory, Pohang (Korea, Republic of)

2011-10-15

After the East-Japan earthquake and the subsequent nuclear disaster, the anti-nuclear mood has been wide spread. It is very unfortunate both for nuclear science community and for the future of mankind, which is threatened by two serious challenges, the global warming caused by the greenhouse effect and the shortage of energy cause by the petroleum exhaustion. While the nuclear energy seemed to be the only solution to these problems, it is clear that it has its own problems, one of which broke out so strikingly in Japan. There are also other problems such as the radiotoxic nuclear wastes that survive up to even tens of thousands years and the limited reserves of Uranium. To solve these problems of nuclear fission energy, accelerator-based sub-critical nuclear reactor was once proposed. (Its details will be explained below.) First of all, it is safe in a disaster such as an earthquake, because the deriving accelerator stops immediately by the earthquake. It also minimizes the nuclear waste problem by reducing the amount of the toxic waste and shortening their half lifetime to only a few hundred years. Finally, it solves the Uranium reserve problem because it can use Thorium as its fuel. The Thorium reserve is much larger than that of Uranium. Although the idea of the accelerator-driven nuclear reactor was proposed long time ago, it has not been utilized yet first by technical difficulty and economical reasons. The accelerator-based system needs 1 GeV, 10 MW power proton accelerator. A conventional linear accelerator would need several hundred m length, which is highly costly particularly in Korea because of the high land cost. However, recent technologies make it possible to realize that scale accelerator by a reasonable size. That is the fixed-field alternating gradient (FFAG) accelerator that is described in this article

Sub-Critical Nuclear Reactor Based on FFAG-Accelerator

International Nuclear Information System (INIS)

Lee, Hee Seok; Kang, Hung Sik; Lee, Tae Yeon

2011-01-01

After the East-Japan earthquake and the subsequent nuclear disaster, the anti-nuclear mood has been wide spread. It is very unfortunate both for nuclear science community and for the future of mankind, which is threatened by two serious challenges, the global warming caused by the greenhouse effect and the shortage of energy cause by the petroleum exhaustion. While the nuclear energy seemed to be the only solution to these problems, it is clear that it has its own problems, one of which broke out so strikingly in Japan. There are also other problems such as the radiotoxic nuclear wastes that survive up to even tens of thousands years and the limited reserves of Uranium. To solve these problems of nuclear fission energy, accelerator-based sub-critical nuclear reactor was once proposed. (Its details will be explained below.) First of all, it is safe in a disaster such as an earthquake, because the deriving accelerator stops immediately by the earthquake. It also minimizes the nuclear waste problem by reducing the amount of the toxic waste and shortening their half lifetime to only a few hundred years. Finally, it solves the Uranium reserve problem because it can use Thorium as its fuel. The Thorium reserve is much larger than that of Uranium. Although the idea of the accelerator-driven nuclear reactor was proposed long time ago, it has not been utilized yet first by technical difficulty and economical reasons. The accelerator-based system needs 1 GeV, 10 MW power proton accelerator. A conventional linear accelerator would need several hundred m length, which is highly costly particularly in Korea because of the high land cost. However, recent technologies make it possible to realize that scale accelerator by a reasonable size. That is the fixed-field alternating gradient (FFAG) accelerator that is described in this article

Antiferromagnetic spintronics of Mn{sub 2}Au: An experiment, first principle, mean field and series expansions calculations study

Energy Technology Data Exchange (ETDEWEB)

Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, 63 46000, Safi (Morocco); LMPHE (URAC 12), Faculty of Science, Mohammed V-Agdal University, Rabat (Morocco); Hlil, E.K. [Institut Néel, CNRS et Université Joseph Fourier, BP 166, F-38042 Grenoble Cedex 9 (France); Hamedoun, M. [Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Benyoussef, A. [LMPHE (URAC 12), Faculty of Science, Mohammed V-Agdal University, Rabat (Morocco); Institute of Nanomaterials and Nanotechnologies, MAScIR, Rabat (Morocco); Hassan II Academy of Science and Technology, Rabat (Morocco); Boutahar, A.; Lassri, H. [LPMMAT, Université Hassan II-Casablanca, Faculté des Sciences, BP 5366 Maârif (Morocco)

2015-11-01

The self-consistent ab initio calculations, based on DFT (Density Functional Theory) approach and using FLAPW (Full potential Linear Augmented Plane Wave) method, are performed to investigate both electronic and magnetic properties of the Mn{sub 2}Au. Polarized spin and spin–orbit coupling are included in calculations within the framework of the antiferromagnetic state between two adjacent Mn plans. Magnetic moment considered to lie along (110) axes are computed. Obtained data from ab initio calculations are used as input for the high temperature series expansions (HTSEs) calculations to compute other magnetic parameters. The exchange interactions between the magnetic atoms Mn–Mn in Mn{sub 2}Au are given by using the experiment results and the mean field theory. The High Temperature Series Expansions (HTSEs) of the magnetic susceptibility with the magnetic moments in Mn{sub 2}Au (m{sub Mn}) is given up to tenth order series in, 1/k{sub B}T. The Néel temperature T{sub N} is obtained by HTSEs combined with the Padé approximant method. The critical exponent associated with the magnetic susceptibility is deduced as well. - Highlights: • The both electronic and magnetic properties of the Mn{sub 2}Au are studied. • The exchange interactions between the magnetic atoms Mn–Mn in Mn{sub 2}Au are given. • The Néel temperature T{sub N} of Mn{sub 2}Au is obtained by HTSEs method. • The critical exponent associated with the magnetic susceptibility is deduced.

Influence of the constant load sintering on the improvement of the transport critical current in Ag-(Bi,Pb)[sub 2]Sr[sub 2]Ca[sub 2]Cu[sub 3]O[sub x] tape form conductor

Energy Technology Data Exchange (ETDEWEB)

Jackiewicz, J [IRC in Superconductivity, Univ. of Cambridge (United Kingdom); Glowacki, B A [IRC in Superconductivity, Univ. of Cambridge (United Kingdom) Dept. of Materials Science and Metallurgy, Univ. of Cambridge (United Kingdom)

1993-05-10

The effects of the short time, low value constant load pressing process of cold rolled silver clad wires conducted at temperatures close to the partial melting point of the ceramic core, from 800 C to 866 C on the microstructure and critical current anisotropy have been studied in detail. The strong influence of the constant load sintering at up to 2 MPa for 1 hour on the improvement of the alignment of the ceramic core in the tape form conductors was confirmred by microstructure investigations and also by the I[sub c] versus [mu][sub 0]H measurements. The magnetic field dependence of the transport critical current, for [mu][sub 0]H parallel to the surface of the tape and also for [mu][sub 0]H perpendicular to the surface of the tape, is very significantly reduced in the tapes sintered under constant load. The analysis of the mechanical creep of silver and ceramic core versus temperature allowed us to optimise the densification conditions of the investigated single core Ag-''2223'' tape form conductor for the load used. (orig.)

Consistency of neutron cross-section data, S /SUB N/ calculations, and measured tritium production for a 14-MeV neutron-driven sphere of natural lithium deuteride

International Nuclear Information System (INIS)

Reupke, W.A.; Davidson, J.N.; Muir, D.W.

1982-01-01

The authors present algorithms, describe a computer program, and gives a computational procedure for the statistical consistency analysis of neutron cross-section data, S /SUB N/ calculations, and measured tritium production in 14-MeV neutron-driven integral assemblies. Algorithms presented include a reduced matrix manipulation technique suitable for manygroup, 14-MeV neutron transport calculations. The computer program incorporates these algorithms and is expanded and improved to facilitate analysis of such integral experiments. Details of the computational procedure are given for a natural lithium deuteride experiment performed at the Los Alamos National Laboratory. Results are explained in terms of calculated cross-section sensitivities and uncertainty estimates. They include a downward adjustment of the 7 Li(n,xt) 14-MeV cross section from 328 + or - 22 to 284 + or - 24 mb, which is supported by the trend of recent differential and integral measurements. It is concluded that with appropriate refinements, the techniques of consistency analysis can be usefully applied to the analysis of 14-MeV neutron-driven tritium production integral experiments

Calculational assessment of critical experiments with mixed-oxide fuel pin arrays moderated by organic solution

International Nuclear Information System (INIS)

Smolen, G.R.; Funabashi, H.

1987-01-01

Critical experiments have been conducted with organically moderated mixed-oxide (MOX) fuel pin assemblies at the Pacific Northwest Lab. Critical Mass Lab. These experiments are part of a joint exchange program between the US Dept. of Energy and the Power Reactor and Nuclear Fuel Development Corp. of Japan in the area of criticality data development. The purpose of these experiments is to benchmark computer codes and cross-section libraries and to assess the reactivity difference between systems moderated by water and those moderated by an organic solution. Past studies have indicated that some organic mixtures may be better moderators than water. This topic is of particular importance to the criticality safety of fuel processing plants where fissile material is dissolved in organic solutions during the solvent extraction process. In the past, it has been assumed that the codes and libraries benchmarked with water-moderated experiments were adequate when performing design and licensing studies of organically moderated systems. Calculations presented in this paper indicated that the Scale code system and the 27-energy-group cross-section library accurately compute k/sub eff/ for organically moderated MOX fuel pin assemblies. Furthermore, the reactivity of an organic solution with a 32 vol % TBP/68 vol% NPH mixture in a heterogeneous configuration is the same, for practical purposes, as water

Demand-Driven Success: Designing Your PDA Experiment

OpenAIRE

Hillen, Charles; Johnson-Grau, Glenn

2012-01-01

Initiating demand-driving acquisition is daunting. Implications for developing a sustainable budget model, choosing a vendor, controlling metadata, monitoring purchases and developing invoice workflows are significant areas of concern that require determinative planning. From mid-February through August 2011, Loyola Marymount University conducted a pilot using demand-driven acquisition; the result of this successful experiment was the library’s decision to fully integrate this purchasing mode...

Re-evaluation of the criticality experiments of the ''Otto Hahn Nuclear Ship'' reactor

Energy Technology Data Exchange (ETDEWEB)

Lengar, I.; Snoj, L.; Rogan, P.; Ravnik, M. [Jozef Stefan Institute, Ljubljana (Slovenia)

2008-11-15

Several series of experiments with a FDR reactor (advanced pressurized light water reactor) were performed in 1972 in the Geesthacht critical facility ANEX. The experiments were performed to test the core prior to its usage for the propulsion of the first German nuclear merchant ship ''Otto-Hahn''. In the present paper a calculational re-evaluation of the experiments is described with the use of the up-to date computer codes (Monte-Carlo code MCNP5) and nuclear data (ENDF/B-VI release 6). It is focused on the determination of uncertainties in the benchmark model of the experimental set-up, originating mainly from the limited set of information still available about the experiments. Effects of the identified uncertainties on the multiplication factor were studied. The sensitivity studies include parametric variation of material composition and geometry. The combined total uncertainty being found 0.0050 in k{sub eff}, the experiments are qualified as criticality safety benchmark experiments. (orig.)

Safety physics inter-comparison of advanced concepts of critical reactors and ADS

International Nuclear Information System (INIS)

Slessarev, I.

2001-01-01

Enhanced safety based on the principle of the natural ''self-defence'' is one of the most desirable features of innovative nuclear systems (critical or sub-critical) regarding both TRU transmutation and ''clean'' energy producer concepts. For the evaluation of the ''self-defence'' domain, the method of the asymptotic reactivity balance has been generalised. The promising option of Hybrids systems (that use a symbiosis of fission and spallation in sub-critical cores) which could benefit the advantages of both Accelerated Driven Systems of the traditional type and regular critical systems, has been advocated. General features of Hybrid dynamics have been presented and analysed. It was demonstrated that an external neutron source of Hybrids can expand the inherent safety potential significantly. This analysis has been applied to assess the safety physics potential of innovative concepts for prospective nuclear power both for energy producers and for transmutation. It has been found, that safety enhancement goal defines a choice of sub-criticality of Hybrids. As for energy producers with Th-fuel cycle, a significant sub-criticality level is required due to a necessity of an improvement of neutronics together with safety enhancement task. (author)

Heat Transfer Experiment with Supercritical CO{sub 2} Flowing Upward in a Circular Tube

Energy Technology Data Exchange (ETDEWEB)

Kim, Hyung Rae; Kim, Hwan Yeol; Song, Jin Ho; Kim, Hee Dong; Bae, Yoon Yeong [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

2005-07-01

SCWR (SuperCritical Water-cooled Reactor) is one of the six reactor candidates selected in the Gen-IV project, which aims at the development of new reactors with enhanced economy and safety. Heat transfer experiments under supercritical conditions are required in relevant geometries for the proper prediction of thermo-hydraulic phenomena in a reactor core. A heat transfer test loop, named as SPHINX (Supercritical Pressure Heat Transfer Investigation for NeXt generation), has been constructed in KAERI. The loop uses carbon dioxide as a surrogate fluid for water since the critical pressure and temperature of CO{sub 2} are much lower those of water. As a first stage of heat transfer experiments, a single tube test is being performed in the test loop. Controlled parameters for the tests are operating pressure, mass flux, and heat flux. Wall temperatures are measured along the tube. Experimental data are compared with existing correlations.

Record critical current densities in IG processed bulk YBa{sub 2}Cu{sub 3}O{sub y} fabricated using ball-milled Y{sub 2}Ba{sub 1}Cu{sub 1}O{sub 5} phase

Energy Technology Data Exchange (ETDEWEB)

Muralidhar, Miryala; Kenta, Nakazato; Murakami, Masato [Department of Materials Science and Engineering, Superconducting Materials Laboratory, Shibaura Institute of Technology, Tokyo (Japan); Zeng, XianLin; Koblischka, Michael R. [Institute of Experimental Physics, Saarland University, Saarbruecken (Germany); Diko, Pavel [Institute of Experimental Physics, Material Physics Laboratory, Slovak Academy of Sciences, Kosice (Slovakia)

2016-02-15

The infiltration-growth (IG) technique enables the uniform and controllable Y{sub 2}BaCuO{sub 5} (Y211) secondary phase particles formation within the YBa{sub 2}Cu{sub 3}O{sub y} (Y123) matrix. Recent results clarified that the flux pinning performance of the Y123 material was dramatically improved by optimizing the processing conditions during the IG process. In this paper, we adapted the IG technique and produced several samples with addition of nanometer-sized Y211 secondary phase particles, which were produced by a ball milling technique. We found that the performance of the IG processed Y123 material dramatically improved in the low field region for a ball milling time of 12 h as compared to the samples without a ball milling step. Magnetization measurements showed a sharp superconducting transition with an onset T{sub c} at around 92 K. The critical current density (J{sub c}) at 77 K and zero field was determined to be 224 022 Acm{sup -2}, which is higher than the not ball-milled sample. Furthermore, microstructural observations exhibited a uniform microstructure with homogenous distribution of nanosized Y-211 inclusions within the Y-123 matrix. The improved performance of the Y-123 material can be understood in terms of fine distribution of the secondary phases. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Comparison of a Shastry-Sutherland lattice stability in Ce{sub 2}Pd{sub 2}Sn as a function of field and doping

Energy Technology Data Exchange (ETDEWEB)

Sereni, Julian G, E-mail: jsereni@cab.cnea.gov.ar [Low Temperature Div., CAB-CNEA and CONICET, 8400 S.C. de Bariloche (Argentina)

2011-01-01

A comparative study of the stability of a Shastry-Sutherland lattice (SSL) in Ce{sub 2}Pd{sub 2}Sn under different physical conditions is presented. Applied magnetic field suppresses the SSL of stoichiometric Ce{sub 2}Pd{sub 2}Sn in a magnetic critical point at T{sub cr}(B) = 4.2K and B{sub cr} = 0.13 T, whereas 25% of Ni does it at T{sub cr}(Ni) = 3.4 K. Electronic concentration variation, driven by the increase of Pd (holes) concentration in Ce{sub 2}Pd{sub 2+y}In{sub 1-y}, decreases the magnetic transition down to T{sub M} = 2.8 K in the limit of the alloy solubility, i.e. y = 0.4. The existence of a M(B) plateau in SSL predicted by theory and the crossing of those isotherms, previously observed in the model compound SrCu{sub 2}(BO{sub 3}){sub 2} are analyzed.

Characteristics of membrane fouling in submerged membrane bioreactor under sub-critical flux operation.

Science.gov (United States)

Su, Y C; Huang, C P; Pan, Jill R; Lee, H C

2008-01-01

Recently, the membrane bioreactor (MBR) process has become one of the novel technologies to enhance the performance of biological treatment of wastewater. Membrane bioreactor process uses the membrane unit to replace a sediment tank, and this can greatly enhance treatment performance. However, membrane fouling in MBR restricts its widespread application because it leads to permeate flux decline, making more frequent membrane cleaning and replacement necessary, which then increases operating and maintenance costs. This study investigated the sludge characteristics in membrane fouling under sub-critical flux operation and also assessed the effect of shear stress on membrane fouling. Membrane fouling was slow under sub-critical flux operation. However, as filamentous microbes became dominant in the reactor, membrane fouling increased dramatically due to the increased viscosity and polysaccharides. A close link was found between membrane fouling and the amount of polysaccharides in soluble EPS. The predominant resistance was the cake resistance which could be minimized by increasing the shear stress. However, the resistance of colloids and solutes was not apparently reduced by increasing shear stress. Therefore, smaller particles such as macromolecules (e.g. polysaccharides) may play an important role in membrane fouling under sub-critical flux operation.

Possible influence of the ferromagnetic/antiferromagnetic interface on the effective critical behavior of bilayers based on La{sub 1−x}Sr{sub x}MnO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Álvarez Miño, Lucero, E-mail: lalvarezm@unal.edu.co [Universidad Nacional de Colombia, Sede Manizales, Cra. 27 #64-60, Manizales (Colombia); Grupo de Superconductividad y Nuevos Materiales, Universidad Nacional de Colombia, Sede Bogotá, Avenida Carrera 30 #45, Bogotá (Colombia); Mulcué-Nieto, Luis Fernando, E-mail: lfmulcuen@unal.edu.co [Laboratorio de Magnetismo y Materiales Avanzados, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Colombia, Sede Manizales, Cra. 27 #64-60, Manizales (Colombia)

2015-03-01

In this work, the effective critical exponent of the spontaneous magnetization, β, and the transition temperature, T{sub C}, were calculated from magnetization measurements of three bilayers based on La{sub 1−x}Sr{sub x}MnO{sub 3} (LSMO). The bilayers structure is a ferromagnetic (FM) LSMO film grown on top of an antiferromagnetic (AF) LSMO film. The value of the antiferromagnetic film thickness was kept the same for the three samples, while the ferromagnetic film had different thickness for each bilayer. Applying a method of calculation based on a linear superposition of the magnetization close to the critical temperature, a β value corresponding to the 3D Ising model was found for the bilayer with the thinnest ferromagnetic film. This result, and the other obtained values are explained taking into account the possible influence of the FM/AF interface on the magnetic and crystal orderings. - Highlights: • The critical exponent β of three LSMO bilayers was determined. • Two bilayers with the thinner FM layer have very similar transition temperature. • Two bilayers with the thinner FM layer have very similar width values. • We have found values of β of the 3D Ising model. • Interface also seems to be responsible for some structural disorder.

Quasi-monoenergetic ion beam acceleration by laser-driven shock and solitary waves in near-critical plasmas

International Nuclear Information System (INIS)

Zhang, W. L.; Qiao, B.; Huang, T. W.; Shen, X. F.; You, W. Y.; Yan, X. Q.; Wu, S. Z.; Zhou, C. T.; He, X. T.

2016-01-01

Ion acceleration in near-critical plasmas driven by intense laser pulses is investigated theoretically and numerically. A theoretical model has been given for clarification of the ion acceleration dynamics in relation to different laser and target parameters. Two distinct regimes have been identified, where ions are accelerated by, respectively, the laser-induced shock wave in the weakly driven regime (comparatively low laser intensity) and the nonlinear solitary wave in the strongly driven regime (comparatively high laser intensity). Two-dimensional particle-in-cell simulations show that quasi-monoenergetic proton beams with a peak energy of 94.6 MeV and an energy spread 15.8% are obtained by intense laser pulses at intensity I_0 = 3 × 10"2"0" W/cm"2 and pulse duration τ = 0.5 ps in the strongly driven regime, which is more advantageous than that got in the weakly driven regime. In addition, 233 MeV proton beams with narrow spread can be produced by extending τ to 1.0 ps in the strongly driven regime.

Polycrystalline magnetic garnet films comprising weakly coupled crystallites for piezoelectrically-driven magneto-optic spatial light modulators

Energy Technology Data Exchange (ETDEWEB)

Mito, S.; Sakurai, H.; Takagi, H.; Inoue, M. [Toyohashi University of Technology, Toyohashi, Aichi 441-8580 (Japan); Baryshev, A. V. [Electronics-Inspired Interdisciplinary Research Institute Toyohashi, Aichi 441-8580 (Japan); Ioffe Physical-Technical Institute, St. Petersburg 194021 (Russian Federation)

2012-04-01

We have investigated the magnetization process of the polycrystalline magnetic garnet films in order to determine the most suitable composition of garnet films for piezoelectrically-driven magneto-optic spatial light modulators (MOSLMs). For experiment, the bismuth-dysprosium-aluminum-substituted yttrium iron (Bi{sub 1.3}Dy{sub 0.7}Y{sub 1.0}Fe{sub 3.1}Al{sub 1.9}O{sub 12}) garnet films were deposited by an RF magnetron sputter and annealed at 700 deg. C in air. The annealing time was varied in a range of several minutes to control the grain size. The saturation magnetization, the remanent magnetization and the composition of the fabricated garnet films slightly changed versus the annealing time. Experiments showed that the coercivity and the grain size increased at longer annealing; the coercivity was larger for films with bigger grains. This work shows that garnet films with smaller coercivity are most suitable for controlling the magnetization of garnet and, correspondingly, the magneto-optical rotation of MOSLM pixels driven by piezoelectrics.

Structural, magnetic, magnetocaloric effect and critical behavior of La{sub 0.7}Sr{sub 0.3−x}□{sub x}MnO{sub 3}(0 ≤ x ≤ 0.05)

Energy Technology Data Exchange (ETDEWEB)

Makni-Chakroun, J., E-mail: makni.jihed@yahoo.fr [LT2S Lab, Digital Research Centre of Sfax, Sfax Technopark, BP 275, 3021 Sakiet-Ezzit (Tunisia); Sfifir, I.; Cheikhrouhou-Koubaa, W.; Koubaa, M. [LT2S Lab, Digital Research Centre of Sfax, Sfax Technopark, BP 275, 3021 Sakiet-Ezzit (Tunisia); Cheikhrouhou, A. [Material Physics Laboratory, Faculty of Sciences of Sfax, B.P. 1171, Sfax University, 3000 Sfax (Tunisia)

2017-06-15

Highlights: • The samples crystallize in the rhombohedral structure with R-3C space group. • Curie temperature T{sub C} decreases with lacuna. • (1/χ) versus temperature indicates Griffiths phase occurrence. • Result show that the paramagnetic-ferromagnetic transition is of second order. • Widom scaling relation confirms the critical exponent value. - Abstract: In this paper, we present the effect of Strontium vacancies on the structure and magnetic properties of La{sub 0.7}Sr{sub 0.3−x}□{sub x}MnO{sub 3} nano-sized compounds (x = 0; 0.01; 0.03 and 0.05), synthesized using the sol-gel method. X-ray diffraction revealed that these manganites crystallized in the rhombohedral structure with space group R3-C. From magnetization measurements as function of temperature and magnetic applied field, we have noticed a large magnetic entropy change (∆S{sub M}) around Curie temperature. ∆S{sub M} is found to decrease with the deficiency content (2.30 J/kg·K for x = 0–1.33 J/kg·K for x = 0.05 under magnetic field change µ{sub 0}∆H = 5 T). This behavior is accompanied by a slight reduction of the Curie temperature (T{sub C} = 338 and 328 K for x = 0 and 0.05, respectively). These results show that our materials are potential candidates for magnetic refrigerants working in above room temperature. The refined values of the critical exponents β, γ and δ obtained from the modified Arrott plots and Kouvel-Fisher method indicated that the behavior of the parent sample and the samples with 1and 3% of strontium-deficient are characterized by long-range mean-field behavior (with β = 0.50; γ = 1). However, for 5% lacuna, the magnetic behavior is close to the theoretical 3D-Heisemberg prediction with short-range exchange coupling.

Search for CPT Violation with the FOCUS Experiment and Measurement of Λ<sub>b> lifetime in the decay Λ<sub>b> → J / Ψ Lambda with the D0 Experiment

Energy Technology Data Exchange (ETDEWEB)

Kryemadhi, Abaz [Indiana Univ., Bloomington, IN (United States)

2004-12-01

This dissertation describes two different projects from two different experiments. We have performed a search for CPT violation in neutral charm meson oscillations using data from the FOCUS Experiment. While flavor mixing in the charm sector is predicted to be small in the Standard Model, it is still possible to investigate CPT violation through a study of the proper time dependence of a CPT asymmetry in right-sign decay rates for D⁰ → K^- π⁺ and $\\bar{D}$⁰ → K⁺π^-. This asymmetry is related to the CPT violating complex parameter ξ and the mixing parameters x and y: A<sub>CPT> ∞ Reξy - Imξx. We determine a 95% confidence level limit of -0.0068 < Reξy - Imξx < 0.0234. Within the framework of the Standard Model Extension incorporating general CPT violation, we also find 95% confidence level limits for the expressions involving coefficients of Lorentz violation of (-2.8 < N(x,y,δ))(Δa<sub>0sub> + 0.6 Δa<sub>Z>< 4.8) x 10^-16 GeV, (-7.0 < N(x,y,δ)Δa<sub>x> < 3.8) x 10^-16 GeV, and (-7.0 < N(x,y,δ)Δa<sub>y> < 3.8) x 10^-16 GeV, where N(x,y,δ) is a normalization factor that incorporates mixing parameters x, y and the doubly Cabibbo suppressed to Cabibbo favored relative strong phase δ.

KNMI DataLab experiences in serving data-driven innovations

Science.gov (United States)

Noteboom, Jan Willem; Sluiter, Raymond

2016-04-01

Climate change research and innovations in weather forecasting rely more and more on (Big) data. Besides increasing data from traditional sources (such as observation networks, radars and satellites), the use of open data, crowd sourced data and the Internet of Things (IoT) is emerging. To deploy these sources of data optimally in our services and products, KNMI has established a DataLab to serve data-driven innovations in collaboration with public and private sector partners. Big data management, data integration, data analytics including machine learning and data visualization techniques are playing an important role in the DataLab. Cross-domain data-driven innovations that arise from public-private collaborative projects and research programmes can be explored, experimented and/or piloted by the KNMI DataLab. Furthermore, advice can be requested on (Big) data techniques and data sources. In support of collaborative (Big) data science activities, scalable environments are offered with facilities for data integration, data analysis and visualization. In addition, Data Science expertise is provided directly or from a pool of internal and external experts. At the EGU conference, gained experiences and best practices are presented in operating the KNMI DataLab to serve data-driven innovations for weather and climate applications optimally.

Research on neutron source multiplication method in nuclear critical safety

International Nuclear Information System (INIS)

Zhu Qingfu; Shi Yongqian; Hu Dingsheng

2005-01-01

The paper concerns in the neutron source multiplication method research in nuclear critical safety. Based on the neutron diffusion equation with external neutron source the effective sub-critical multiplication factor k s is deduced, and k s is different to the effective neutron multiplication factor k eff in the case of sub-critical system with external neutron source. The verification experiment on the sub-critical system indicates that the parameter measured with neutron source multiplication method is k s , and k s is related to the external neutron source position in sub-critical system and external neutron source spectrum. The relation between k s and k eff and the effect of them on nuclear critical safety is discussed. (author)

Understanding hospital meal experiences by means of Participant-Driven-Photo-Elicitation

DEFF Research Database (Denmark)

Justesen, Lise; Mikkelsen, Bent Egberg; Gyimóthy, Szilvia

2014-01-01

A patients’ hospital meal experiences can be complex and often difficult to capture using traditional methods. This study investigated patients’ hospital meal experiences using participant-driven-photo-elicitation (PDPE). PDPE invites respondents to photograph their daily lives and combines this ...

The role of carbonic anhydrase in C<sub>4sub> photosynthesis

Energy Technology Data Exchange (ETDEWEB)

Studer, Anthony [Life Sciences Research Foundation, Baltimore, MD (United States)

2015-10-01

Current pressures on the global food supply have accelerated the urgency for a second green revolution using novel and sustainable approaches to increase crop yield and efficiency. This proposal outlines experiments to address fundamental questions regarding the biology of C<sub>4sub> photosynthesis, the method of carbon fixation utilized by the most productive food, feed and bioenergy crops. Carbonic anhydrase (CA) has been implicated in multiple cellular functions including nitrogen metabolism, water use efficiency, and photosynthesis. CA catalyzes the first dedicated step in C<sub>4sub> photosynthesis, the hydration of CO<sub>2sub> into bicarbonate, and is potentially rate limiting in C<sub>4sub> grasses. Using insertional mutagenesis, we have generated CA mutants in maize, and propose the characterization of these mutants using phenotypic, physiological, and transcriptomic profiling to assay the plant’s response to altered CA activity. In addition, florescent protein tagging experiments will be employed to study the subcellular localization of CA paralogs, providing critical data for modeling carbon fixation in C<sub>4sub> plants. Finally, I propose parallel experiments in Setaria viridis to explore its relevance as model C<sub>4sub> grass. Using a multifaceted approach, this proposal addresses important questions in basic biology, as well as the need for translation research in response to looming global food challenges.

Rational construction of Z-scheme Ag{sub 2}CrO{sub 4}/g-C{sub 3}N{sub 4} composites with enhanced visible-light photocatalytic activity

Energy Technology Data Exchange (ETDEWEB)

Luo, Jin, E-mail: lj328520504@126.com; Zhou, Xiaosong; Ma, Lin; Xu, Xuyao

2016-12-30

Highlights: • Novel visible-light driven Ag{sub 2}CrO{sub 4}/g-C{sub 3}N{sub 4} composites were synthesized. • Ag{sub 2}CrO{sub 4}/g-C{sub 3}N{sub 4} exhibited enhanced visible-light photocatalytic activity. • The reasons for the enhanced photocatalytic activity were revealed. - Abstract: Novel visible-light driven Z-scheme Ag{sub 2}CrO{sub 4}/g-C{sub 3}N{sub 4} composites with different contents of Ag{sub 2}CrO{sub 4} were fabricated by a facile chemical precipitation method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–vis diffuse reflectance spectroscopy (UV-vis DRS), photoluminescence (PL) spectroscopy and photoelectrochemical measurements. Compared with individual g-C{sub 3}N{sub 4} and Ag{sub 2}CrO{sub 4}, the Ag{sub 2}CrO{sub 4}/g-C{sub 3}N{sub 4} composites displayed much larger photocatalytic activities for the photocatalytic degradation of methyl orange (MO) solution at room temperature under visible light irradiation (λ > 420 nm). Importantly, the optimum photodegradation rate constant of the Ag{sub 2}CrO{sub 4}/g-C{sub 3}N{sub 4} composite at a theoretical weight content of 8.0% Ag{sub 2}CrO{sub 4} for the photodegradation of MO was 0.0068 min{sup −1}, which was 5.7 and 4.3 times higher than that of pure g-C{sub 3}N{sub 4} and Ag{sub 2}CrO{sub 4}, respectively. Such enormous enhancement in photocatalytic performance was predominantly ascribed to the efficient separation and transfer of photogenerated electrons and holes at the Ag{sub 2}CrO{sub 4}/g-C{sub 3}N{sub 4} interface imparted through the Z-scheme electron transfer. Furthermore, radical trap experiments depicted that both the holes and superoxide radical anions were thought to dominate oxidative species of the Ag{sub 2}CrO{sub 4}/g-C{sub 3}N{sub 4} composite for MO degradation under visible light irradiation. Ultimately, a tentative Z-scheme photodegradation mechanism

The Q{sup p}{sub Weak} experiment

Energy Technology Data Exchange (ETDEWEB)

Androic, D. [University of Zagreb (Croatia); Armstrong, D. S. [The College of William and Mary (United States); Asaturyan, A. [Yerevan Physics Institute (Armenia); Averett, T. [The College of William and Mary (United States); Balewski, J. [Massachusetts Institute of Technology (United States); Beaufait, J. [Thomas Jefferson National Accelerator Facility (United States); Beminiwattha, R. S. [Ohio University (United States); Benesch, J. [Thomas Jefferson National Accelerator Facility (United States); Benmokhtar, F. [Duquesne University (United States); Birchall, J. [University of Manitoba (Canada); Carlini, R. D.; Cornejo, J. C. [The College of William and Mary (United States); Covrig, S. [Thomas Jefferson National Accelerator Facility (United States); Dalton, M. M. [University of Virginia (United States); Davis, C. A. [TRIUMF (United States); Deconinck, W. [The College of William and Mary (United States); Diefenbach, J. [Hampton University (United States); Dow, K. [Massachusetts Institute of Technology (United States); Dowd, J. F. [The College of William and Mary (United States); Dunne, J. A. [Mississippi State University (United States); and others

2013-03-15

In May 2012, the Q{sup p}{sub Weak} collaboration completed a two year measurement program to determine the weak charge of the proton Q{sub W}{sup p} = ( 1 - 4sin{sup 2}{theta}{sub W}) at the Thomas Jefferson National Accelerator Facility (TJNAF). The experiment was designed to produce a 4.0 % measurement of the weak charge, via a 2.5 % measurement of the parity violating asymmetry in the number of elastically scattered 1.165 GeV electrons from protons, at forward angles. At the proposed precision, the experiment would produce a 0.3 % measurement of the weak mixing angle at a momentum transfer of Q{sup 2} = 0.026 GeV{sup 2}, making it the most precise stand alone measurement of the weak mixing angle at low momentum transfer. In combination with other parity measurements, Q{sup p}{sub Weak} will also provide a high precision determination of the weak charges of the up and down quarks. At the proposed precision, a significant deviation from the Standard Model prediction could be a signal of new physics at mass scales up to Asymptotically-Equal-To 6 TeV, whereas agreement would place new and significant constraints on possible Standard Model extensions at mass scales up to Asymptotically-Equal-To 2 TeV. This paper provides an overview of the physics and the experiment, as well as a brief look at some preliminary diagnostic and analysis data.

Thermal properties and Ising critical behavior in EuFe{sub 2}As{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Oleaga, A., E-mail: alberto.oleaga@ehu.es [Departamento de Física Aplicada I, Escuela Técnica Superior de Ingeniería, Universidad del País Vasco UPV/EHU, Alameda Urquijo s/n, 48013 Bilbao (Spain); Salazar, A. [Departamento de Física Aplicada I, Escuela Técnica Superior de Ingeniería, Universidad del País Vasco UPV/EHU, Alameda Urquijo s/n, 48013 Bilbao (Spain); Thamizhavel, A.; Dhar, S.K. [Department of Condensed Matter Physics and Material Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400 005 (India)

2014-12-25

Highlights: • A high resolution ac photopyroelectric calorimeter is used. • Thermal diffusivity and specific heat are measured at the phase transitions. • Latent heat is exchanged at the Fe{sup 2+} spin-ordering transition. • Eu{sup 2+} spin-ordering transition belongs to the 3D-Ising universality class. - Abstract: Specific heat and thermal diffusivity have been studied by means of a high resolution ac photopyroelectric calorimeter in the vicinity of phase transitions in EuFe{sub 2}As{sub 2}: the first one corresponding to the ordering of the Fe{sup 2+} spins concomitant to a structural transition at 188.1 K and the second one to the antiferromagnetic ordering of the Eu{sup 2+} spins at 18.4 K. The weak first order character of the first transition has been confirmed while the critical behavior of the second transition at lower temperature has been established to correspond to the 3D-Ising universality class (α{sub exp} = 0.11 ± 0.03). This is in agreement with the proposed uniaxial arrangement of the Eu{sup 2+} spins lying along the long orthorhombic axis a as reported in literature.

Sequential coating upconversion NaYF{sub 4}:Yb,Tm nanocrystals with SiO{sub 2} and ZnO layers for NIR-driven photocatalytic and antibacterial applications

Energy Technology Data Exchange (ETDEWEB)

Tou, Meijie; Luo, Zhenguo; Bai, Song; Liu, Fangying; Chai, Qunxia; Li, Sheng; Li, Zhengquan, E-mail: zqli@zjnu.edu.cn

2017-01-01

ZnO is one of the most promising materials for both photocatalytic and antibacterial applications, but its wide bandgap requires the excitation of UV light which limits their applications under visible and NIR bands. Herein, we demonstrate a facile approach to synthesize core-shell-shell hybrid nanoparticles consisting of hexagonal NaYF{sub 4}:Yb,Tm, amorphous SiO{sub 2} and wurtzite ZnO. The upconversion nanocrystals are used as the core seeds and sequentially coated with an insulting shell and a semiconductor layer. Such hybrid nanoparticles can efficiently utilize the NIR light through the upconverting process, and display notable photocatalytic performance and antibacterial activity under NIR irradiation. The developed NaYF{sub 4}:Yb,Tm@SiO{sub 2}@ZnO nanoparticles are characterized with TEM, XRD, EDS, XPS and PL spectra, and their working mechanism is also elucidated. - Highlights: • Core-shell NaYF{sub 4}:Yb,Tm@SiO{sub 2}@TiO{sub 2} NPs were synthesized via a sequential coating method. • Hybrid NaYF{sub 4}:Yb,Tm@SiO{sub 2}@TiO{sub 2} NPs show NIR-light enhanced photocatalytic activity. • NIR-driven antibacterial performance has been realized with NaYF{sub 4}:Yb,Tm@SiO{sub 2}@TiO{sub 2} NPs. • Working mechanism of the hybrid photocatalysts as antibacterial agents was proposed.

The nuclear criticality information system's project to archive unpublished critical experiment data

International Nuclear Information System (INIS)

Koponen, B.L.; Doherty, A.L.; Clayton, E.D.

1991-01-01

Critical experiment facilities produced a large amount of important data during the past forty-five years. However, much useful data remains unpublished. The unpublished material exists in the form of experimenters' logbooks, notes, photographs, material descriptions, etc. These data could be important for computer code validation, understanding the physics of criticality, facility design, or for setting process limits. In the past, criticality specialists have been able to obtain unpublished details by direct contact with the experimenters. The closure of facilities and the loss of personnel is likely to lead to the loss of the facility records unless an effort is made to ensure that the records are preserved. It has been recognized for some time that the unpublished records of critical experiment facilities comprise a valuable resource, thus the Nuclear Criticality Information System (NCIS) is working to ensure that the records are preserved and made available via NCIS. As a first step in the archiving project, we identified criteria to help judge which series of experiments should be considered for archiving. Data that are used for validating calculations or the basis for subcritical limits in standards, handbooks, and guides are of particular importance. In this paper we will discuss the criteria for archiving, the priority list of experiments for archiving, and progress in developing an NCIS image database using current CD-ROM technology. (Author)

An experimental study of high heat flux removal by shear-driven liquid films

Directory of Open Access Journals (Sweden)

Zaitsev Dmitry

2017-01-01

Full Text Available Intensively evaporating liquid films, moving under the friction of a co-current gas flow in a mini-channel (shear-driven liquid films, are promising for the use in cooling systems of modern semiconductor devices with high local heat release. In this work, the effect of various parameters, such as the liquid and gas flow rates and channel height, on the critical heat flux in the locally heated shear-driven water film has been studied. A record value of the critical heat flux of 1200 W/cm2 has been achieved in experiments. Heat leaks to the substrate and heat losses to the atmosphere in total do not exceed 25% for the heat flux above 400 W/cm2. Comparison of the critical heat fluxes for the shear-driven liquid film and for flow boiling in a minichannel shows that the critical heat flux is an order of magnitude higher for the shear-driven liquid film. This confirms the prospect of using shear-driven liquid films in the modern high-efficient cooling systems.

Search on neutrino oscillation {nu}{sub {mu}}{yields}{nu}{sub e} in the NOMAD experiment; Recherches des oscillations de neutrinos {nu}{sub {mu}}{yields}{nu}{sub e} dans l`experience NOMAD

Energy Technology Data Exchange (ETDEWEB)

Valuev, Viatcheslav [Paris-7 Univ., 75 (France)

1998-07-07

The NOMAD experiment is a search for neutrino oscillations using the large band neutrino beams of SPS at CERN. It is dealing with the two oscillation modes: {nu}{sub {mu}}{yields}{nu}{sub {tau}} and {nu}{sub {mu}}{yields}{nu}{sub e}. This thesis presents the results obtained in the search of oscillations {nu}{sub {mu}}{yields}{nu}{sub e} with the data produced by NOMAD in 1995 and 1996. The first two chapters deal with the short presentation of the neutrino oscillation phenomenology and a summary of the experimental situation. The third chapter describes the experimental setup of the NOMAD detector at CERN, designed to identify the interactions of {nu}{sub e} by means of the charged current. This is done with the transition radiation detector (TRD) designed to separate the electrons from pions with a rejection factor higher then 1000 at an electron efficiency of 90%, in the 1 - 50 GeV region. Details about the TRD operation are given in chapter four. The fifth chapter gives the algorithms of electron-pion separation as well as their performances. The last two chapters present the analysis of the {nu}{sub {mu}}{yields}{nu}{sub e} data obtained in 1995 and 1996 and the final results. The conclusion is that the available data give no evidence for the neutrino oscillations. The upper limit obtained for the mixing angle is sin{sup 2}(2{theta}) < 1.3 {center_dot} 10{sup -3} (90% C.L.). This result eliminates completely the oscillation region of LSND experiment (Liquid Scintillator Neutrino Detector) at LAMPF for {Delta}m{sup 2} > 15 eV{sup 2} and gives the most constraining world limit on sin{sup 2}(2{theta}) for {Delta}m{sup 2} > 20 eV{sup 2} 123 refs., 82 figs., 37 tabs.

CLUMPED LIGHT WATER MODERATED UO$sub 2$ SUPERHEAT CRITICALS. PART II. ANALYSIS

Energy Technology Data Exchange (ETDEWEB)

Petersen, G. T.

1963-11-15

Critical and subcritical reactivity measurements on an EVESR-type core, using EVESR UO/sub 2/ superheat fuel elements, are analyzed in order to obtain a physics design model for use in the EVESR. (T.F.H.)

Validation of the code ETOBOX/BOXER for UO2 LWR lattices based on the experiments TRX, BAPL-UO2 and other critical experiments

International Nuclear Information System (INIS)

Paratte, J.M.

1985-07-01

The EIR codes system for LWR arrays is based on cross sections taken out of ENDF/B-4 and ENDF/B-5 by the code ETOBOX. The calculation method for the arrays (code BOXER) and the cross sections as well were applied to the CSEWG benchmark experiments TRX-1 to 4 and BAPL-UO/sub 2/-1 to 3. The results are compared to the measured values and to some calculations of other institutions as well. This demonstrates that the deviations of the parameters calculated by BOXER are typical for the cross sections used. A large number of critical experiments were calculated using the measured material bucklings in order to bring to light possible trends in the calculation of the multiplication factor k/sub eff/. First it came out that the error bounds of B/sub m//sup 2/ evalu-ated in the measurements are often optimistic. Two-dimensional calculations improved the results of the cell calculations. With a mean scattering of 4 to 5 mk in the normal arrays, the multiplication factors calculated by BOXER are satisfactory. However one has to take into account a slight trend of k/sub eff/ to grow with the moderator to fuel ratio and the enrichment. (author)

Time-Dependent S{sub N} Calculations Describing Pulsed Source Experiments at the FRO Reactor

Energy Technology Data Exchange (ETDEWEB)

Bergstrom, A.; Kockum, J.; Soderberg, S. [Research Institute of National Defence, Stockholm (Sweden)

1968-04-15

In view of the difficulties in describing pulsed source experiments quantitatively in assemblies consisting of a fast core and a light reflector, a time-dependent S{sub N} code has been applied to this type of assembly. The code, written for the IBM 7090 computer, divides time into short intervals and computes the flux in spherical geometry for each interval using the Carlson S{sub N} scheme. The source term is obtained by extrapolation from two earlier time-intervals. Several problems in connection with the discretization of the time, space and energy dimensions are discussed. For the sub-critical assembly studied the treatment of the lower energy-groups is decisive for the numerical stability. A 22-group cross-section set with a low energy cut-off at 0.04 eV obtained with the SPENG programme has been used. The time intervals are varied continuously and are set proportional to the inverse of the maximum logarithmic time-derivative of the space and energy-dependent flux with the further restriction that they are not allowed to increase above a predetermined value. In a typical case, the intervals vary between 10{sup -9} and 10{sup -8} sec. The memory of the computer is fully exploited when 22 energy groups and 46 radial points are used. The computing time for each time-interval is about 6 sec. The code has been applied to a 3.5% sub-critical assembly consisting of a 20% enriched, spherical uranium metal core with a thick copper reflector and the calculations have been compared to experiments with good agreement. The calculations show that spectral equilibrium below 10 keV is not reached until times long compared to the usual measuring times and that the exponential decay finally reached is entirely determined by reflector properties at almost thermal energies. It is also shown that the simple one- and two-region models are inadequate in this case and that no time-independent prompt neutron life-time can be obtained from the measurements. (author)

Safety physics inter-comparison of advanced concepts of critical reactors and ADS

Energy Technology Data Exchange (ETDEWEB)

Slessarev, I. [CEA Cadarache, 13 - Saint-Paul-lez-Durance (France). Dept. d' Etudes des Reacteurs

2001-07-01

Enhanced safety based on the principle of the natural ''self-defence'' is one of the most desirable features of innovative nuclear systems (critical or sub-critical) regarding both TRU transmutation and ''clean'' energy producer concepts. For the evaluation of the ''self-defence'' domain, the method of the asymptotic reactivity balance has been generalised. The promising option of Hybrids systems (that use a symbiosis of fission and spallation in sub-critical cores) which could benefit the advantages of both Accelerated Driven Systems of the traditional type and regular critical systems, has been advocated. General features of Hybrid dynamics have been presented and analysed. It was demonstrated that an external neutron source of Hybrids can expand the inherent safety potential significantly. This analysis has been applied to assess the safety physics potential of innovative concepts for prospective nuclear power both for energy producers and for transmutation. It has been found, that safety enhancement goal defines a choice of sub-criticality of Hybrids. As for energy producers with Th-fuel cycle, a significant sub-criticality level is required due to a necessity of an improvement of neutronics together with safety enhancement task. (author)

Sexual violence and sub-Saharan migrants in Morocco: a community-based participatory assessment using respondent driven sampling.

Science.gov (United States)

Keygnaert, Ines; Dialmy, Abdessamad; Manço, Altay; Keygnaert, Jeroen; Vettenburg, Nicole; Roelens, Kristien; Temmerman, Marleen

2014-05-08

The European Union contracted Morocco to regulate migration from so-called “transit migrants” from Morocco to Europe via the European Neighbourhood Policy. Yet, international organisations signal that human, asylum and refugee rights are not upheld in Morocco and that many sub-Saharan migrants suffer from ill-health and violence. Hence, our study aimed at 1) investigating the nature of violence that sub-Saharan migrants experience around and in Morocco, 2) assessing which determinants they perceive as decisive and 3) formulating prevention recommendations. Applying Community-Based Participatory Research, we trained twelve sub-Saharan migrants as Community Researchers to conduct in-depth interviews with peers, using Respondent Driven Sampling. We used Nvivo 8 to analyse the data. We interpreted results with Community Researchers and the Community Advisory Board and commonly formulated prevention recommendations. Among the 154 (60 F-94 M) sub-Saharan migrants interviewed, 90% reported cases of multiple victimizations, 45% of which was sexual, predominantly gang rape. Seventy-nine respondents were personally victimized, 41 were forced to witness how relatives or co-migrants were victimized and 18 others knew of peer victimisation. Severe long lasting ill-health consequences were reported while sub-Saharan victims are not granted access to the official health care system. Perpetrators were mostly Moroccan or Algerian officials and sub-Saharan gang leaders who function as unofficial yet rigorous migration professionals at migration ‘hubs’. They seem to proceed in impunity. Respondents link risk factors mainly to their undocumented and unprotected status and suggest that migrant communities set-up awareness raising campaigns on risks while legal and policy changes enforcing human rights, legal protection and human treatment of migrants along with severe punishment of perpetrators are politically lobbied for. Sub-Saharan migrants are at high risk of sexual

Evaluation of the 252Cf-source-driven neutron noise analysis method for measuring the subcriticality of LWR fuel storage casks

International Nuclear Information System (INIS)

Mihalczo, J.T.

1987-01-01

The 252 Cf-source-driven neutron noise analysis method was evaluated to determine if it could be used to measure the subcriticality of storage casks of burnt LWR fuel submerged in fuel storage pools, fully loaded and as they are being loaded. The motivation for this evaluation was that measurements of k/sub eff/ would provide the parameter most directly related to the criticality safety of storage cask configurations of LWR fuel and could allow proper credit for fuel burnup without reliance on calculations. This in turn could lead to more cost-effective cask designs. Evaluation of the method for this application was based on (1) experiments already completed at a critical experiments facility using arrays of PWR fuel pins typical of the size of storage cask configurations, (2) the existence of neutron detectors that can function in shipping cask environments, and (3) the ability to construct ionization chambers containing 252 Cf of adequate intensity for these measurements. These three considerations are discussed

Determination of the solid surface critical exponent β{sub 1} from contact-angle variation on approach to a wetting transition: Cyclohexane/aniline/quartz

Energy Technology Data Exchange (ETDEWEB)

Pallas, Norman R., E-mail: Sam-7-iam@hotmail.com [BP Research Centre Warrensville, 4440 Warrensville Center Road, Cleveland, Ohio 44128 (United States)

2016-03-21

The three-phase contact angle (θ) for the system cyclohexane/aniline/quartz has been measured from drop shapes as a function of temperature on approach to the cyclohexane/aniline upper consolute solution temperature T{sub c}. The experiments employed exacting criteria previously established for thermodynamic-quality measurements at fluid interfaces. A first-order wetting transition from partial wetting to complete wetting was observed at a temperature T{sub w}, 2.12 K below T{sub c}. The contact angle vanishes at T{sub w}, scaling as cos θ ∼ |T − T{sub c}|{sup β{sub 1}−μ} for T < T{sub w} and cos θ = 1.0 for T{sub w} < T < T{sub c}. The experimental results give a value for β{sub 1} = 0.74 ± 0.03, in agreement with theoretical calculations. The data clearly rule out higher order contributions to the change in the contact angle near the critical point for this system. These results are in marked contrast to previous measurements on this system from measurements of capillary rise and meniscus curvature.

The influence of different diffusion pattern to the sub- and super-critical fluid flow in brown coal

Science.gov (United States)

Peng, Peihuo

2018-03-01

Sub- and super-critical CO2 flowing in nanoscale pores are recently becoming of great interest due to that it is closely related to many engineering applications, such as geological burial and sequestration of carbon dioxide, Enhanced Coal Bed Methane recovery ( ECBM), super-critical CO2 fracturing and so on. Gas flow in nanopores cannot be described simply by the Darcy equation. Different diffusion pattern such as Fick diffusion, Knudsen diffusion, transitional diffusion and slip flow at the solid matrix separate the seepage behaviour from Darcy-type flow. According to the principle of different diffusion pattern, the flow of sub- and super-critical CO2 in brown coal was simulated by numerical method, and the results were compared with the experimental results to explore the contribution of different diffusion pattern and swelling effect in sub- and super-critical CO2 flow in nanoscale pores.

ICSBEP-2007, International Criticality Safety Benchmark Experiment Handbook

International Nuclear Information System (INIS)

Blair Briggs, J.

2007-01-01

1 - Description: The Critically Safety Benchmark Evaluation Project (CSBEP) was initiated in October of 1992 by the United Sates Department of Energy. The project quickly became an international effort as scientist from other interested countries became involved. The International Criticality Safety Benchmark Evaluation Project (ICSBEP) is now an official activity of the Organization of Economic Cooperation and Development - Nuclear Energy Agency (OECD-NEA). This handbook contains criticality safety benchmark specifications that have been derived from experiments that were performed at various nuclear critical facilities around the world. The benchmark specifications are intended for use by criticality safety engineers to validate calculational techniques used to establish minimum subcritical margins for operations with fissile material. The example calculations presented do not constitute a validation of the codes or cross section data. The work of the ICSBEP is documented as an International Handbook of Evaluated Criticality Safety Benchmark Experiments. Currently, the handbook spans over 42,000 pages and contains 464 evaluations representing 4,092 critical, near-critical, or subcritical configurations and 21 criticality alarm placement/shielding configurations with multiple dose points for each and 46 configurations that have been categorized as fundamental physics measurements that are relevant to criticality safety applications. The handbook is intended for use by criticality safety analysts to perform necessary validations of their calculational techniques and is expected to be a valuable tool for decades to come. The ICSBEP Handbook is available on DVD. You may request a DVD by completing the DVD Request Form on the internet. Access to the Handbook on the Internet requires a password. You may request a password by completing the Password Request Form. The Web address is: http://icsbep.inel.gov/handbook.shtml 2 - Method of solution: Experiments that are found

Criticality experiment for No.2 core of DF-VI fast neutron criticality facility

International Nuclear Information System (INIS)

Yang Lijun; Liu Zhenhua; Yan Fengwen; Luo Zhiwen; Chu Chun; Liang Shuhong

2007-01-01

At the completion of the DF-VI fast neutron criticality facility, its core changed, and it was restarted and a series of experiments and measurements were made. According to the data from 29 criticality experiments, the criticality element number and mass were calculated, the control rod reactivity worth were measured by period method and rod compensate method, reactivity worth of safety rod and safety block were measured using reactivity instrument; the reactivity worth of outer elements and radial distribution of elements were measured too. Based on all the measurements mentioned above, safety operation parameters for core 2 in DF-VI fast neutron criticality facility were conformed. (authors)

The impact and applicability of critical experiment evaluations

Energy Technology Data Exchange (ETDEWEB)

Brewer, R. [Los Alamos National Lab., NM (United States)

1997-06-01

This paper very briefly describes a project to evaluate previously performed critical experiments. The evaluation is intended for use by criticality safety engineers to verify calculations, and may also be used to identify data which need further investigation. The evaluation process is briefly outlined; the accepted benchmark critical experiments will be used as a standard for verification and validation. The end result of the project will be a comprehensive reference document.

What's so critical about Critical Neuroscience? Rethinking experiment, enacting critique.

Science.gov (United States)

Fitzgerald, Des; Matusall, Svenja; Skewes, Joshua; Roepstorff, Andreas

2014-01-01

In the midst of on-going hype about the power and potency of the new brain sciences, scholars within "Critical Neuroscience" have called for a more nuanced and sceptical neuroscientific knowledge-practice. Drawing especially on the Frankfurt School, they urge neuroscientists towards a more critical approach-one that re-inscribes the objects and practices of neuroscientific knowledge within webs of social, cultural, historical and political-economic contingency. This paper is an attempt to open up the black-box of "critique" within Critical Neuroscience itself. Specifically, we argue that limiting enactments of critique to the invocation of context misses the force of what a highly-stylized and tightly-bound neuroscientific experiment can actually do. We show that, within the neuroscientific experiment itself, the world-excluding and context-denying "rules of the game" may also enact critique, in novel and surprising forms, while remaining formally independent of the workings of society, and culture, and history. To demonstrate this possibility, we analyze the Optimally Interacting Minds (OIM) paradigm, a neuroscientific experiment that used classical psychophysical methods to show that, in some situations, people worked better as a collective, and not as individuals-a claim that works precisely against reactionary tendencies that prioritize individual over collective agency, but that was generated and legitimized entirely within the formal, context-denying conventions of neuroscientific experimentation. At the heart of this paper is a claim that it was precisely the rigors and rules of the experimental game that allowed these scientists to enact some surprisingly critical, and even radical, gestures. We conclude by suggesting that, in the midst of large-scale neuroscientific initiatives, it may be "experiment", and not "context", that forms the meeting-ground between neuro-biological and socio-political research practices.

Program of nuclear criticality safety experiment at JAERI

International Nuclear Information System (INIS)

Kobayashi, Iwao; Tachimori, Shoichi; Takeshita, Isao; Suzaki, Takenori; Ohnishi, Nobuaki

1983-11-01

JAERI is promoting the nuclear criticality safety research program, in which a new facility for criticality safety experiments (Criticality Safety Experimental Facility : CSEF) is to be built for the experiments with solution fuel. One of the experimental researches is to measure, collect and evaluate the experimental data needed for evaluation of criticality safety of the nuclear fuel cycle facilities. Another research area is a study of the phenomena themselves which are incidental to postulated critical accidents. Investigation of the scale and characteristics of the influences caused by the accident is also included in this research. The result of the conceptual design of CSEF is summarized in this report. (author)

Criticality safety assessment of FBTR fuel sub-assemblies using WIMS cross section set

International Nuclear Information System (INIS)

Gupta, H.C.; Chakraborty, B.

2002-01-01

Full text: FBTR's irradiated fuel sub-assemblies (FSAs) are sent to RML at Indira Gandhi Centre for Atomic Research for post irradiation examination. The FSAs are cut open and the fuel pins are separated for examination in the hot cells. It was required to evaluate the criticality safety in handling the FSAs in the hot cells. Criticality safety studies for handling two as well as three irradiated FSAs in the hot cells under dry conditions were carried out by the Safety Group at IGCAR, Kalpakkam. Monte Carlo code KENO (Version Va) which uses 16-group Hansen-Roach cross-section set was used for the calculations. Subsequently, during the safety review of the proposition by the Safety Review Committee (SARCOP) of AERB, it was stipulated to carry out the criticality safety studies under flooded condition also. We carried out the criticality safety studies for these fuel sub assemblies in different configurations under dry (buried in concrete) as well as wet condition (flooded with light water) using Monte Carlo codes MONALI (developed at BARC) and KENO4 using WlMS-69 group cross section set. Results of our analyses under various conditions are presented in this paper

Hierarchical Bi{sub 2}WO{sub 6} architectures decorated with Pd nanoparticles for enhanced visible-light-driven photocatalytic activities

Energy Technology Data Exchange (ETDEWEB)

Zhang, Jinniu; Chen, Tianhua [School of Physics and Information Technology, Shaanxi Normal University, Xi’an, 710062 (China); Lu, Hongbing, E-mail: hblu@snnu.edu.cn [School of Physics and Information Technology, Shaanxi Normal University, Xi’an, 710062 (China); Yang, Zhibo; Yin, Feng; Gao, Jianzhi; Liu, Qianru [School of Physics and Information Technology, Shaanxi Normal University, Xi’an, 710062 (China); Tu, Yafang [Department of Physics, Institute for Interdisciplinary Research, Jianghan University, Wuhan, 430056 (China)

2017-05-15

Highlights: • A new kind of Pd decorated Bi{sub 2}WO{sub 6} hierarchical microarchitecture was synthesized. • Pd nanoparticles remarkably improved the photocatalytic activity of Bi{sub 2}WO{sub 6}. • The photo-generated holes and ·O{sub 2}{sup −} played a crucial role in the degradation of RhB. • The photocatalytic enhancement mechanism of the Pd-Bi{sub 2}WO{sub 6} composites was proposed. - Abstract: A new kind of hierarchical Pd-Bi{sub 2}WO{sub 6} architecture decorated with different molar ratios of Pd to Bi, has been fabricated by a hydrothermal process, followed by a chemical deposition method. The photocatalytic activities of the pure Bi{sub 2}WO{sub 6} and Pd-Bi{sub 2}WO{sub 6} nanocatalyst were examined in the degradation of Rhodamine B (RhB) dyes and phenol under visible light. The photocatalytic results showed that the Pd-Bi{sub 2}WO{sub 6} nanocomposites possessed observably enhanced photocatalytic activities. Particularly, the 2.0% Pd loaded Bi{sub 2}WO{sub 6} had the highest photocatalytic activity, exhibiting a nearly complete degradation of 30 mg/L RhB and 10 mg/L phenol within only 50 and 60 min, respectively. In addition, the trapping experiment results indicated that the photo-generated holes (h{sup +}) and ·O{sub 2}{sup −} played a crucial role in the degradation of RhB. According to the experimental results, the photocatalytic degradation mechanism of Pd-Bi{sub 2}WO{sub 6} was also proposed. The enhanced photocatalytic activities were ascribed to the combined effects of the highly efficient separation of electrons and holes, improved visible light utilization and increased BET specific surface areas of the Pd-Bi{sub 2}WO{sub 6} nanocomposites.

Critical mass experiment using U-235 foils and lucite plates

International Nuclear Information System (INIS)

Sanchez, R.; Butterfield, K.; Kimpland, R.; Jaegers, P.

1998-01-01

The main objective of this experiment was to show how the multiplication of the system increases as moderated material is placed between highly enriched uranium foils. In addition, this experiment served to demonstrate the hand-stacking techniques, and approach to criticality by remote operation. This experiment was designed by Tom McLaughlin in the mid seventies as part of the criticality safety course that is taught at Los Alamos Critical Experiment Facility (LACEF). The W-U-235 ratio for this experiment was 215 which is where the minimum critical mass for this configuration occurs

Critical mass experiment using 235U foils and lucite plates

International Nuclear Information System (INIS)

Sanchez, R.; Butterfield, K.; Kimpland, R.; Jaegers, P.

1998-01-01

This experiment demonstrated how the neutron multiplication of a system increases as moderated material is placed between highly enriched uranium foils. In addition, this experiment served to demonstrate the hand-stacking technique and approach to criticality be remote operation. This experiment was designed by McLaughlin in the mid-seventies as part of the criticality safety course that is taught at the Los Alamos Critical Experiments Facility. The H/ 235 U ratio for this experiment was 215, which is the ratio at which the minimum critical mass for this configuration occurs

Laser-driven ICF experiments: Laboratory Report No. 223

International Nuclear Information System (INIS)

McCrory, R.L.

1991-04-01

Laser irradiation uniformity is a key issue and is treated in some detail. The basic irradiation uniformity requirements and practical ways of achieving these requirements are both discussed, along with two beam-smoothing techniques: induced spatial incoherence (ISI), and smoothing by spectral dispersion (SSD). Experiments to measure and control the irradiation uniformity are also highlighted. Following the discussion of irradiation uniformity, a brief review of coronal physics is given, including the basic physical processes and their experimental signatures, together with a summary of pertinent diagnostics and results from experiments. Methods of determining ablation rates and thermal transport are also described. The hydrodynamics of laser-driven targets must be fully understood on the basis of experiments. Results from implosion experiments, including a brief description of the diagnostics, are presented. Future experiments aimed at determining ignition scaling and demonstrating hydrodynamically equivalent physics applicable to high-gain designs

Experiments on the basic behavior of supercritical CO{sub 2} natural circulation

Energy Technology Data Exchange (ETDEWEB)

Liu, Guangxu [CNNC Key Laboratory on Nuclear Reactor Thermal Hydraulics Technology, Nuclear Power Institute of China (China); Huang, Yanping, E-mail: hyanping007@163.com [CNNC Key Laboratory on Nuclear Reactor Thermal Hydraulics Technology, Nuclear Power Institute of China (China); Wang, Junfeng; Lv, Fa [CNNC Key Laboratory on Nuclear Reactor Thermal Hydraulics Technology, Nuclear Power Institute of China (China); Leung, Laurence K.H. [Canadian Nuclear Laboratories, 286 Plant Road, Chalk River, Ontario (Canada)

2016-04-15

Highlights: • Steady-state behavior of supercritical CO{sub 2} natural circulation was studied. • Effects of pressure and inlet temperature were carefully investigated. • No instabilities were found in present study. • The maximum of mass flow was obtained at outlet temperature much higher than T{sub pc}. • Inlet temperature has vital effect on mass flow rate. - Abstract: To study the steady-state characteristics of supercritical carbon dioxide natural circulation, experiments were carried out in a simple rectangular loop with vertically placed heating section. The effects of system pressure and inlet temperature on the system behavior were also investigated. No instabilities were found in the present experiments. The maximum of mass flow rate was obtained at a heating section outlet temperature much higher than the pseudo-critical temperature. The maximum value of mass flow rate increased with system pressure just as in two-phase natural circulation systems. Inlet temperature significantly affected the steady-state characteristics of supercritical carbon dioxide natural circulation system. A small temperature difference of 14 °C in the natural circulation system could induce a mass flow rate with considerably high Re up to 9.1 × 10{sup 4}, which indicates the potential for supercritical carbon dioxide to be used as a high efficient natural circulation working fluid.

Microstructural and crystallographic imperfections of MgB{sub 2} superconducting wire and their correlation with the critical current density

Energy Technology Data Exchange (ETDEWEB)

Shahabuddin, Mohammed; Alzayed, Nasser S. [Department of Physics and Astronomy, College of Science, P. O. Box 2455, King Saud University, Riyadh 11451 (Saudi Arabia); Oh, Sangjun [Materials Research Team, National Fusion Research Institute, Yueeong, Daejeon 305-333 (Korea, Republic of); Choi, Seyong [Busan Center, Korea Basic Science Institute, Geumjeong, Busan 609-735 (Korea, Republic of); Maeda, Minoru [Department of Physics, College of Science and Technology, Nihon University, 1-8 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8308 (Japan); Hata, Satoshi; Shimada, Yusuke [Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1 Kasugakoen, Kasuga, Fukuoka 816-8580 (Japan); Hossain, Md Shahriar Al [Institute for Superconducting and Electronic Materials, University of Wollongong, North Wollongong, New South Wales 2500 (Australia); Kim, Jung Ho, E-mail: jhk@uow.edu.au [Department of Physics and Astronomy, College of Science, P. O. Box 2455, King Saud University, Riyadh 11451 (Saudi Arabia); Institute for Superconducting and Electronic Materials, University of Wollongong, North Wollongong, New South Wales 2500 (Australia)

2014-01-15

A comprehensive study of the effects of structural imperfections in MgB{sub 2} superconducting wire has been conducted. As the sintering temperature becomes lower, the structural imperfections of the MgB{sub 2} material are increased, as reflected by detailed X-ray refinement and the normal state resistivity. The crystalline imperfections, caused by lattice disorder, directly affect the impurity scattering between the π and σ bands of MgB{sub 2}, resulting in a larger upper critical field. In addition, low sintering temperature keeps the grain size small, which leads to a strong enhancement of pinning, and thereby, enhanced critical current density. Owing to both the impurity scattering and the grain boundary pinning, the critical current density, irreversibility field, and upper critical field are enhanced. Residual voids or porosities obviously remain in the MgB{sub 2}, however, even at low sintering temperature, and thus block current transport paths.

Sensitivity-Uncertainty Techniques for Nuclear Criticality Safety

Energy Technology Data Exchange (ETDEWEB)

Brown, Forrest B. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Rising, Michael Evan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Alwin, Jennifer Louise [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-08-07

The sensitivity and uncertainty analysis course will introduce students to k<sub>eff> sensitivity data, cross-section uncertainty data, how k<sub>eff> sensitivity data and k<sub>eff> uncertainty data are generated and how they can be used. Discussion will include how sensitivity/uncertainty data can be used to select applicable critical experiments, to quantify a defensible margin to cover validation gaps and weaknesses, and in development of upper subcritical limits.

Microstructure study of electrochemically driven Li{sub x}Si

Energy Technology Data Exchange (ETDEWEB)

Son, Seoung-Bum [Department of Materials Science and Engineering, Seoul National University, Seoul, 151-742 (Korea, Republic of); Department of Mechanical Engineering, University of Colorado at Boulder, Boulder, CO, 80309 (United States); Trevey, James E.; Dunn, Martin L.; Lee, Se-Hee [Department of Mechanical Engineering, University of Colorado at Boulder, Boulder, CO, 80309 (United States); Roh, Hyunchul; Kim, Sung-Hwan; Han, Heung Nam; Oh, Kyu Hwan [Department of Materials Science and Engineering, Seoul National University, Seoul, 151-742 (Korea, Republic of); Kim, Kee-Bum [Department of Materials Science and Engineering, Seoul National University, Seoul, 151-742 (Korea, Republic of); High Temperature Energy Materials Research Center, Korea Institute of Science and Technology, Seoul, 136-791 (Korea, Republic of); Cho, Jong Soo [Department of Materials Science and Engineering, Seoul National University, Seoul, 151-742 (Korea, Republic of); MK Electron, 316-2 Geumeo-ri, Pogok-myeon, Yongin-si, Gyeong gi-do, 449-810 (Korea, Republic of); Moon, Jeong-Tak [MK Electron, 316-2 Geumeo-ri, Pogok-myeon, Yongin-si, Gyeong gi-do, 449-810 (Korea, Republic of); DeLuca, Christopher M.; Maute, Kurt K. [Department of Aerospace Engineering Sciences, University of Colorado, CB 429, Boulder, CO, 80301-0429 (United States)

2011-11-15

We report the direct observation of microstructural changes of Li{sub x}Si electrode with lithium insertion. HRTEM experiments confirm that lithiated amorphous silicon forms a shell around a core made up of the unlithiated silicon and that fully lithiated silicon contains a large number of pores of which concentration increases toward the center of the particle. Chemomechanical modeling is employed in order to explain this mechanical degradation resulting from stresses in the Li{sub x}Si particles with lithium insertion. Because lithiation-induced volume expansion and pulverization are the key mechanical effects that plague the performance and lifetime of high-capacity Si anodes in lithium-ion batteries, our observations and chemomechanical simulation provide important mechanistic insight for the design of advanced battery materials. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Magnetic field-aligned plasma expansion in critical ionization velocity space experiments

International Nuclear Information System (INIS)

Singh, N.

1989-01-01

Motivated by the recent Critical Ionization Velocity (CIV) experiments in space, the temporal evolution of a plasma cloud released in an ambient plasma is studied. Time-dependent Vlasov equations for both electrons and ions, along with the Poisson equation for the self-consistent electric field parallel to the ambient magnetic field, are solved. The initial cloud is assumed to consist of cold, warm, and hot electrons with temperatures T/sub c/ ≅ 0.2 eV, T/sub w/ ≅ 2 eV, and T/sub h/ ≅ 10 eV, respectively. It is found that the minor hot electrons escape the cloud, and their velocity distribution function shows the typical time-of-flight dispersion feature - that is, the larger the distance from the cloud, the larger is the average drift velocity of the escaping electrons. The major warm electrons expand along the magnetic field line with the corresponding ion-acoustic speed. The combined effect of the escaping hot electrons and the expanding warm ones sets up an electric potential structure which accelerates the ambient electrons into the cloud. Thus, the energy loss due to the electron escape is partly replenished. The electric field distribution in the potential structure depends on the stage of the evolution; before the rarefaction waves propagating from the edges of the cloud reach its center, the electric fields point into the cloud. After this stage the cloud divides into two subclouds, with each having their own bipolar electric fields. Effects of collisions on the evolution of plasma clouds are also discussed. The relevance of the results seen from the calculations are discussed in the context of recent space experiments on CIV

Experimental Determination of the Neutron Characteristics of UO{sub 2}-PuO{sub 2}-H{sub 2}O Lattices; Determination Experimentale Des Caracteristiques Neutroniques De Reseaux UO{sub 2}-PuO{sub 2}-H{sub 2}O

Energy Technology Data Exchange (ETDEWEB)

Debrue, J.; Fabry, A.; Leenders, L.; Motte, F.; Van Den Broeck, H. [Centre d' Etude de l' Energie Nucleaire, Mol (Belgium)

1967-09-15

As part of the investigation, in the VENUS test facility, of the variably moderated core of the BR3/VULCAIN reactor, a fuel assembly consisting of 37 UO{sub 2}-PuO{sub 2} pins (94% natural UO{sub 2}, 6% PuO{sub 2} ) was substituted for one of the enriched (to 7% {sup 235}U) UO{sub 2} fuel assemblies constituting the reactor core. Experiments were carried out with the object of refining the mathematical models for calculating the performance of this special assembly; inter alia, the fission density distribution and the changing ratio of the effective cross-sections for fission in the {sup 233}Pu and {sup 235}U were measured. Using the same critical facility, the authors are carrying out a critical experiment related directly to the problems of plutonium recycling in pressurized light-water thermal reactors. Three types of fuel are being used: UO{sub 2}-PuO{sub 2} with 3% {sup 235}U and 1% fissile plutonium, UO{sub 2}-PuO{sub 2} with 2% {sup 235}U and 2% fissile plutonium, and UO{sub 2} with 4% {sup 235}U. The two UO{sub 2}-PuO{sub 2} mixtures have completely different isotopic contents of {sup 240}Pu: 7% and 17%. In the first part of the experimental programme, a study is being made of regular lattices in cores having two co-axial cylindrical zones: a UO{sub 2}-PuO{sub 2} zone and a UO{sub 2} zone. Particular attention is being paid to investigating the region on either side of the interface separating the two zones, where the neutron spectrum reflects the characteristic energy distributions in each of the two lattices. The experimental results are to be used in calibrating the computational methods. In the second part of the experimental programme, parts of the core of the SENA power reactor will be simulated with a view to studying the problems of reloading one third of the core with mixed UO{sub 2}-PuO{sub 2} fuel. Among the experimental techniques employed in these various experiments emphasis is given to those most specifically related to the presence of

Recovery of Organic and Amino Acids from Sludge and Fish Waste in Sub Critical Water Conditions

Directory of Open Access Journals (Sweden)

Muhammad Faisal

2011-12-01

Full Text Available The possibility of organic and amino acid production from the treatment of sludge and fish waste using water at sub critical conditions was investigated. The results indicated that at sub-critical conditions, where the ion product of water went through a maximum, the formation of organic acids was favorable. The presence of oxidant favored formation of acetic and formic acid. Other organic acids of significant amount were propionic, succinic and lactic acids. Depending on the type of wastes, formation of other organic acids was also possible. Knowing the organic acids obtained by hydrolysis and oxidation in sub-critical water of various wastes are useful in designing of applicable waste treatment process, complete degradation of organic wastes into volatile carbon and water, and also on the viewpoint of resource recovery. The production of lactic acid was discussed as well. The results indicated that temperature of 573 K, with the absence of oxidant, yield of lactic acid from fish waste was higher than sewage sludge. The maximum yield of total amino acids (137 mg/g-dry fish from waste fish entrails was obtained at subcritical condition (T = 523 K, P = 4 MPa at reaction time of 60 min by using the batch reactor. The amino acids obtained in this study were mainly alanine and glycine. Keywords:  organic acids, amino acids, sub-critical water, hydrothermal, resources recovery

Gate-controlled metal-insulator transition in the LaAlO{sub 3}/SrTiO{sub 3} system with sub-critical LaAlO{sub 3} thickness

Energy Technology Data Exchange (ETDEWEB)

Lee, Joon Sung; Lee, Seung Ran; Chang, Jung-Won; Noh, Hyunho; Baasandorj, Lkhagvasuren; Shim, Seung-Bo; Kim, Jinhee [Korea Research Institute of Standards and Science, Daejeon 305-600 (Korea, Republic of); Seung, Sang Keun; Shin, Hyun Sup; Song, Jonghyun [Department of Physics, Chungnam National University, Daejeon 305-764 (Korea, Republic of)

2012-12-15

We studied the electrical conduction in the LaAlO{sub 3}/SrTiO{sub 3} (LAO/STO) interface electron system with a sub-critical LAO layer thickness of {proportional_to}3.5 unit cells (uc). It was found that the true dividing point between metallic and insulating behaviour without gating lies near the LAO thickness of 3.5 uc. Our marginally metallic 3.5 uc sample showed a sharp transition to insulating state at temperatures which strongly depended on the applied negative back-gate voltage. The superior gate-controllability of the sample was attributed to its sheet carrier density which was an order of magnitude lower than those of conducting LAO/STO samples with 4 uc or more of LAO layers. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

International handbook of evaluated criticality safety benchmark experiments

International Nuclear Information System (INIS)

2010-01-01

The Criticality Safety Benchmark Evaluation Project (CSBEP) was initiated in October of 1992 by the United States Department of Energy. The project quickly became an international effort as scientists from other interested countries became involved. The International Criticality Safety Benchmark Evaluation Project (ICSBEP) became an official activity of the Organization for Economic Cooperation and Development - Nuclear Energy Agency (OECD-NEA) in 1995. This handbook contains criticality safety benchmark specifications that have been derived from experiments performed at various nuclear critical facilities around the world. The benchmark specifications are intended for use by criticality safety engineers to validate calculational techniques used to establish minimum subcritical margins for operations with fissile material and to determine criticality alarm requirement and placement. Many of the specifications are also useful for nuclear data testing. Example calculations are presented; however, these calculations do not constitute a validation of the codes or cross section data. The evaluated criticality safety benchmark data are given in nine volumes. These volumes span over 55,000 pages and contain 516 evaluations with benchmark specifications for 4,405 critical, near critical, or subcritical configurations, 24 criticality alarm placement / shielding configurations with multiple dose points for each, and 200 configurations that have been categorized as fundamental physics measurements that are relevant to criticality safety applications. Experiments that are found unacceptable for use as criticality safety benchmark experiments are discussed in these evaluations; however, benchmark specifications are not derived for such experiments (in some cases models are provided in an appendix). Approximately 770 experimental configurations are categorized as unacceptable for use as criticality safety benchmark experiments. Additional evaluations are in progress and will be

Analytical solution of point kinetic equations for sub-critical systems

International Nuclear Information System (INIS)

Henrice Junior, Edson; Goncalves, Alessandro C.

2013-01-01

This article presents an analytical solution for the set of point kinetic equations for sub-critical reactors. This solution stems from the ordinary, non-homogeneous differential equation that rules the neutron density and that presents the incomplete Gamma function in its functional form. The method used proved advantageous and allowed practical applications such as the linear insertion of reactivity, considering an external constant source or with both varying linearly. (author)

Experiment study about phase transition characteristics of CO{sub 2} in low-permeable porous media

Energy Technology Data Exchange (ETDEWEB)

Guo, P.; Wang, J.; Luo, Y. [State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu (China); Southwest Petroleum Univ., Chengdu (China); Fan, J.M. [PetroChina, Xian (China). Ultra-low Permeability Reservoir Research Inst.

2009-07-01

This paper described an experimental study conducted to characterize phase changes in carbon dioxide (CO{sub 2}) that occur during CO{sub 2} sequestration and enhanced oil recovery (EOR) processes. An ultrasonic testing method was used to determine the influence of pressure and temperature on core fluids. Phase transitions were characterized by collecting time series of ultrasonic signals in a data acquisition system and calculating the correlation dimension of the phase space. A correlation dimension analysis method was used with a fractal theory to develop correlation curves for the phase transition characteristics of CO{sub 2} in porous media. The study demonstrated that below a critical temperature, the existence of porous media can increase the phase transition point of CO{sub 2}. Above the critical temperature, the existence of porous media decreased the inflection point in the pressure-volume relationship curve for CO{sub 2}. Time difference changes were also more apparent above the critical temperature. 11 refs., 2 tabs., 11 figs.

Anisotropy of critical current density in the superconducting Nb/sub 3/Sn tape wires

Energy Technology Data Exchange (ETDEWEB)

Glowacki, B A [Technical Univ., Wroclaw (Poland). Inst. of Fundamental Electrotechnics and Electrotechnology

1985-04-01

In this letter the results are presented of an investigation of Isub(c parallel) and Isub(c perpendicular) in Nb/sub 3/Sn layers obtained in the process diffusion of tin atoms from liquid bronze solution Cu-80% Sn to the Nb-1.5% Zr substrate. Measurements of critical current density in Nb/sub 3/Sn layers were carried out in a perpendicular magnetic field of the induction value 4.25 T for different sample surface orientations in relation to the magnetic field strength vector defined by the value of angle. The critical current density was measured at a temperature of 4.2 K. Phase identification and investigation of the microstructure of superconducting Nb-Sn layers were performed on the Moessbauer spectrometer and scanning electron microscope, respectively. Classification measurements of grains in Nb-Sn layers were carried out with TV automatic image analyser. The texture and lattice parameter in Nb/sub 3/Sn layers were investigated by means of an X-ray diffractometer. The surface zone of Nb/sub 3/Sn layer was removed with the use of an argon ion gun. Results are presented and discussed.

Reactor physics experiment plan using TCA

Energy Technology Data Exchange (ETDEWEB)

Shimada, Shoichiro [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

2000-06-01

The Reduced-Moderation Water Reactor (RMWR) is one of the next generation water-cooled reactors, which aims at effective utilization of uranium resource, high burn-up, long operation cycle, and plutonium multi-recycle. For verification of the feasibility, negative void reactivity coefficient and conversion ratio more than 1.0 must be confirmed. This report is to plan critical experiments using TCA in JAERI. Critical Experiments performed so far in Europe and Japan are reviewed, and no useful data are available for RMWR development. Critical experiments using TCA (Tank Type Critical Assembly) in JAERI are planned. MOX fuel rods should be prepared for the experiments and some modifications of equipment are needed for use of MOX fuel rods. This report describes the preliminary plan of physics experiments. The number of MOX-fuel rods used in the experiments is obtained by calculations and modification of the equipment for the experiments are shown. New MOX fuel and UO{sub 2} fuel rods are necessary for the RMWR critical experiments. Number of MOX fuel rods is 1000 for Plutonium fissile enrichment of 5 wt%, 1000 for 10 wt%, 1500 for 15 wt% and 500 for 20 wt%, respectively. Depleted UO{sub 2} fuel rods for blanket/buffer region are 4000. Driver fuel rods of 4.9 wt% UO{sub 2} are 3000. Modification of TCA facility is requested to treat the large amount of MOX fuels from safety point of view. Additional shielding device at the top of the tank for loading the MOX fuels and additional safety plates to ensure safety are requested. The core is divided into two regions by inserting an inner tank to avoid criticality in MOX region only. The test region is composed by MOX fuel rods in the inner tank. Criticality is established by UO{sub 2} driver fuel rods outside of the inner tank. (Tsuchihashi, K.)

Review of studies on criticality safety evaluation and criticality experiment methods

International Nuclear Information System (INIS)

Naito, Yoshitaka; Yamamoto, Toshihiro; Misawa, Tsuyoshi; Yamane, Yuichi

2013-01-01

Since the early 1960s, many studies on criticality safety evaluation have been conducted in Japan. Computer code systems were developed initially by employing finite difference methods, and more recently by using Monte Carlo methods. Criticality experiments have also been carried out in many laboratories in Japan as well as overseas. By effectively using these study results, the Japanese Criticality Safety Handbook was published in 1988, almost the intermediate point of the last 50 years. An increased interest has been shown in criticality safety studies, and a Working Party on Nuclear Criticality Safety (WPNCS) was set up by the Nuclear Science Committee of Organisation Economic Co-operation and Development in 1997. WPNCS has several task forces in charge of each of the International Criticality Safety Benchmark Evaluation Program (ICSBEP), Subcritical Measurement, Experimental Needs, Burn-up Credit Studies and Minimum Critical Values. Criticality safety studies in Japan have been carried out in cooperation with WPNCS. This paper describes criticality safety study activities in Japan along with the contents of the Japanese Criticality Safety Handbook and the tasks of WPNCS. (author)

A demonstration experiment of steam-driven, high-pressure melt ejection

International Nuclear Information System (INIS)

Allen, M.D.; Pitch, M.; Nichols, R.T.

1990-08-01

A steam blowdown test was performed at the Surtsey Direct Heating Test Facility to test the steam supply system and burst diaphragm arrangement that will be used in subsequent Surtsey Direct Containment Heating (DCH) experiments. Following successful completion of the steam blowdown test, the HIPS-10S (High-Pressure Melt Streaming) experiment was conducted to demonstrate that the technology to perform steam-driven, high-pressure melt ejection (HPME) experiments has been successfully developed. In addition, the HIPS-10S experiment was used to assess techniques and instrumentation design to create the proper timing of events in HPME experiments. This document discusses the results of this test

Structural transition in Mo{sub 3}Sb{sub 7} probed by muon spin relaxation

Energy Technology Data Exchange (ETDEWEB)

Tabata, Y. [Department of Materials Science and Engineering, Kyoto University, Kyoto 606-8501 (Japan); Koyama, T.; Kohara, T. [Graduate School of Material Science, University of Hyogo, Kamigori, Ako-gun, Hyogo 678-1297 (Japan); Watanabe, I. [Advanced Meson Science Laboratory, RIKEN Nishina Center, Wako, Saitama 351-0198 (Japan); Nakamura, H., E-mail: h.nakamura@ht8.ecs.kyoto-u.ac.j [Department of Materials Science and Engineering, Kyoto University, Kyoto 606-8501 (Japan)

2009-04-15

Longitudinal-field muSR measurements have been made for Mo{sub 3}Sb{sub 7} focusing on the nature of the structural transition recently found at T{sub S}approx =50K. Taking account of a critical behavior of the relaxation rate lambda at approxT{sub S}, together with the motional narrowing of the nuclear dipolar field revealed in a zero-field experiment, and the tetragonal lattice symmetry lowering below T{sub S}, we propose long-range order of spin-singlet dimers, i.e., the formation of the valence bond crystal below T{sub S}. As a possible origin, the frustration in the interdimer antiferromagnetic interaction is suggested.

Critical thickness of high structural quality SrTiO{sub 3} films grown on orthorhombic (101) DyScO{sub 3}.

Energy Technology Data Exchange (ETDEWEB)

Biegalski, M. D.; Trolier-McKinstry, S.; Nelson, C. T.; Schlom, D. G.; Fong, D. D.; Eastman, J. A.; Fuoss, P. H.; Streiffer, S. K.; Heeg, T.; Schubert, J.; Tian, W.; Pan, X. Q.; Hawley, M. E.; Bernhagen, M.; Reiche, P.; Uecker, R.; Pennsylvania State Univ.; Forschungszentrum Julich; Univ. Michigan; LANL; Max-Born-Strabe

2008-12-01

Strained epitaxial SrTiO{sub 3} films were grown on orthorhombic (101) DyScO{sub 3} substrates by reactive molecular-beam epitaxy. The epitaxy of this substrate/film combination is cube on cube with a pseudocubic out-of-plane (001) orientation. The strain state and structural perfection of films with thicknesses ranging from 50 to 1000 {angstrom} were examined using x-ray scattering. The critical thickness at which misfit dislocations was introduced was between 350 and 500 {angstrom}. These films have the narrowest rocking curves (full width at half maximum) ever reported for any heteroepitaxial oxide film (0.0018{sup o}). Only a modest amount of relaxation is seen in films exceeding the critical thicknesses even after postdeposition annealing at 700 C in 1 atm of oxygen. The dependence of strain relaxation on crystallographic direction is attributed to the anisotropy of the substrate. These SrTiO{sub 3} films show structural quality more typical of semiconductors such as GaAs and silicon than perovskite materials; their structural relaxation behavior also shows similarity to that of compound semiconductor films.

Study on the method of determining the sub-criticality of a reactor via the measurement of core neutron flux spatial distribution

International Nuclear Information System (INIS)

Ma Aifeng; Jiang Xiaofeng; Zhang Shaohong

2007-01-01

A new methodology based on rigorous reactor physics theory astead of the point reactor assumption was proposed to determine or monitor the sub-criticality ora reactor, especially the sub-critical reactor of ADS, via the measurement of in-core flux spatial distribution. Preliminary numerical studies on the 1st ADS sub-critical experimental facilities-Venus No.1 in China have demonstrated the feasibility of this new method. Related discussions pointed out the potential applications of the method. (authors)

Experimental investigation on flow patterns of RP-3 kerosene under sub-critical and supercritical pressures

Science.gov (United States)

Wang, Ning; Zhou, Jin; Pan, Yu; Wang, Hui

2014-02-01

Active cooling with endothermic hydrocarbon fuel is proved to be one of the most promising approaches to solve the thermal problem for hypersonic aircraft such as scramjet. The flow patterns of two-phase flow inside the cooling channels have a great influence on the heat transfer characteristics. In this study, phase transition processes of RP-3 kerosene flowing inside a square quartz-glass tube were experimentally investigated. Three distinct phase transition phenomena (liquid-gas two phase flow under sub-critical pressures, critical opalescence under critical pressure, and corrugation under supercritical pressures) were identified. The conventional flow patterns of liquid-gas two phase flow, namely bubble flow, slug flow, churn flow and annular flow are observed under sub-critical pressures. Dense bubble flow and dispersed flow are recognized when pressure is increased towards the critical pressure whilst slug flow, churn flow and annular flow disappear. Under critical pressure, the opalescence phenomenon is observed. Under supercritical pressures, no conventional phase transition characteristics, such as bubbles are observed. But some kind of corrugation appears when RP-3 transfers from liquid to supercritical. The refraction index variation caused by sharp density gradient near the critical temperature is thought to be responsible for this corrugation.

TRIGA criticality experiment for testing burn-up calculations

International Nuclear Information System (INIS)

Persic, Andreja; Ravnik, Matjaz; Zagar, Tomaz

1999-01-01

A criticality experiment with partly burned TRIGA fuel is described. 20 wt % enriched standard TRIGA fuel elements initially containing 12 wt % U are used. Their average burn-up is 1.4 MWd. Fuel element burn-up is calculated in 2-D four group diffusion approximation using TRIGLAV code. The burn-up of several fuel elements is also measured by reactivity method. The excess reactivity of several critical and subcritical core configurations is measured. Two core configurations contain the same fuel elements in the same arrangement as were used in the fresh TRIGA fuel criticality experiment performed in 1991. The results of the experiment may be applied for testing the computer codes used for fuel burn-up calculations. (author)

Los Alamos Critical Experiments Facility

International Nuclear Information System (INIS)

Malenfant, R.E.

1991-01-01

The Critical Experiments Facility of the Los Alamos National Laboratory has been in existence for 45 years. In that period of time, thousands of measurements have been made on assemblies containing every fissionable material in various configurations that included bare metal and compounds of the nitrate, sulfate, fluoride, carbide, and oxide. Techniques developed or applied include Rossi-α, source-jerk, rod oscillator, and replacement measurements. Many of the original measurements of delay neutrons were performed at the site, and a replica of the Hiroshima weapon was operated at steady state to assist in evaluating the relative biological effectiveness (RBE) of neutrons. Solid, liquid, and gas fissioning systems were run at critical. Operation of this original critical facility has demonstrated the margin of safety that can be obtained through remote operation. Eight accidental excursions have occurred on the site, ranging from 1.5 x 10 16 to 1.2 x 10 17 fissions, with no significant exposure to personnel or damage to the facility beyond the machines themselves -- and in only one case was the machine damaged beyond further use. The present status of the facility, operating procedures, and complement of machines will be described in the context of programmatic activity. New programs will focus on training, validation of criticality alarm systems, experimental safety assessment of process applications, and dosimetry. Special emphasis will be placed on the incorporation of experience from 45 years of operation into present procedures and programs. 3 refs

Pramana – Journal of Physics | Indian Academy of Sciences

Indian Academy of Sciences (India)

This includes computer codes for burnup studies based on transport theory and Monte Carlo methods, codes for studying the kinetics of ADS and sub-critical facilities driven by 14 MeV neutron generators for ADS experiments and development of sub-criticality measurement methods. The paper discusses the physics issues ...

Ternary g-C{sub 3}N{sub 4}/ZnO/AgCl nanocomposites: Synergistic collaboration on visible-light-driven activity in photodegradation of an organic pollutant

Energy Technology Data Exchange (ETDEWEB)

Akhundi, Anise; Habibi-Yangjeh, Aziz, E-mail: ahabibi@uma.ac.ir

2015-12-15

Graphical abstract: - Highlights: • Novel ternary g-C{sub 3}N{sub 4}/ZnO/AgCl nanocomposites were prepared using a facile method. • g-C{sub 3}N{sub 4}/ZnO/AgCl (40%) has superior activity in degradation of RhB under visible-light. • The activity is 7.5 and 6-fold higher than g-C{sub 3}N{sub 4}/ZnO and g-C{sub 3}N{sub 4}/AgCl, respectively. • There are synergistic collaboration between ZnO and AgCl in enhancing the activity. - Abstract: The present work demonstrates the preparation of ternary g-C{sub 3}N{sub 4}/ZnO/AgCl nanocomposites, as novel visible-light-driven photocatalysts, using a facile large-scale methodology. The microstructure, morphology, purity, thermal, and spectroscopic properties of the prepared samples were studied using XRD, TEM, EDX, TG, UV–vis DRS, FT-IR, and PL techniques. Compared with the g-C{sub 3}N{sub 4}/ZnO and g-C{sub 3}N{sub 4}/AgCl nanocomposites, the g-C{sub 3}N{sub 4}/ZnO/AgCl nanocomposites displayed higher photocatalytic activity for degradation of rhodamine B under visible-light irradiation. Photocatalytic activity of the g-C{sub 3}N{sub 4}/ZnO/AgCl (40%) nanocomposite is about 9.5, 7.5, and 6-fold higher than those of the g-C{sub 3}N{sub 4}, g-C{sub 3}N{sub 4}/ZnO, and g-C{sub 3}N{sub 4}/AgCl samples, respectively. The enhanced photocatalytic activity of the nanocomposites was mainly attributed to efficiently separation of the charge carriers by synergistic collaboration of ZnO and AgCl in removing photogenerated electrons from g-C{sub 3}N{sub 4}. Furthermore, the results showed that the photocatalytic activity of the nanocomposite considerably depends on the preparation time, calcination temperature, and scavengers of the reactive species. Finally, the nanocomposite was found to be a reusable photocatalyst.

Battery-Powered RF Pre-Ionization System for the Caltech Magnetohydrodynamically-Driven Jet Experiment: RF Discharge Properties and MHD-Driven Jet Dynamics

Science.gov (United States)

Chaplin, Vernon H.

This thesis describes investigations of two classes of laboratory plasmas with rather different properties: partially ionized low pressure radiofrequency (RF) discharges, and fully ionized high density magnetohydrodynamically (MHD)-driven jets. An RF pre-ionization system was developed to enable neutral gas breakdown at lower pressures and create hotter, faster jets in the Caltech MHD-Driven Jet Experiment. The RF plasma source used a custom pulsed 3 kW 13.56 MHz RF power amplifier that was powered by AA batteries, allowing it to safely float at 4-6 kV with the cathode of the jet experiment. The argon RF discharge equilibrium and transport properties were analyzed, and novel jet dynamics were observed. Although the RF plasma source was conceived as a wave-heated helicon source, scaling measurements and numerical modeling showed that inductive coupling was the dominant energy input mechanism. A one-dimensional time-dependent fluid model was developed to quantitatively explain the expansion of the pre-ionized plasma into the jet experiment chamber. The plasma transitioned from an ionizing phase with depressed neutral emission to a recombining phase with enhanced emission during the course of the experiment, causing fast camera images to be a poor indicator of the density distribution. Under certain conditions, the total visible and infrared brightness and the downstream ion density both increased after the RF power was turned off. The time-dependent emission patterns were used for an indirect measurement of the neutral gas pressure. The low-mass jets formed with the aid of the pre-ionization system were extremely narrow and collimated near the electrodes, with peak density exceeding that of jets created without pre-ionization. The initial neutral gas distribution prior to plasma breakdown was found to be critical in determining the ultimate jet structure. The visible radius of the dense central jet column was several times narrower than the axial current channel

Medical Education to Enhance Critical Consciousness: Facilitators' Experiences.

Science.gov (United States)

Zaidi, Zareen; Vyas, Rashmi; Verstegen, Danielle; Morahan, Page; Dornan, Tim

2017-11-01

To analyze educators' experiences of facilitating cultural discussions in two global health professions education programs and what these experiences had taught them about critical consciousness. A multicultural research team conducted in-depth interviews with 16 faculty who had extensive experience facilitating cultural discussions. They analyzed transcripts of the interviews thematically, drawing sensitizing insights from Gramsci's theory of cultural hegemony. Collaboration and conversation helped the team self-consciously examine their positions toward the data set and be critically reflexive. Participant faculty used their prior experience facilitating cultural discussions to create a "safe space" in which learners could develop critical consciousness. During multicultural interactions they recognized and explicitly addressed issues related to power differentials, racism, implicit bias, and gender bias. They noted the need to be "facile in attending to pain" as learners brought up traumatic experiences and other sensitive issues including racism and the impact of power dynamics. They built relationships with learners by juxtaposing and exploring the sometimes-conflicting norms of different cultures. Participants were reflective about their own understanding and tendency to be biased. They aimed to break free of such biases while role modeling how to have the courage to speak up. Experience had given facilitators in multicultural programs an understanding of their responsibility to promote critical consciousness and social justice. How faculty without prior experience or expertise could develop those values and skills is a topic for future research.

Partially-reflected water-moderated square-piteched U(6.90)O<sub>2sub> fuel rod lattices with 0.67 fuel to water volume ratio (0.800 CM Pitch)

Energy Technology Data Exchange (ETDEWEB)

Harms, Gary A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2015-09-01

The US Department of Energy (DOE) Nuclear Energy Research Initiative funded the design and construction of the Seven Percent Critical Experiment (7uPCX) at Sandia National Laboratories. The start-up of the experiment facility and the execution of the experiments described here were funded by the DOE Nuclear Criticality Safety Program. The 7uPCX is designed to investigate critical systems with fuel for light water reactors in the enrichment range above 5% ²³⁵U. The 7uPCX assembly is a water-moderated and -reflected array of aluminum-clad square-pitched U(6.90%)O<sub>2sub> fuel rods.

Handbook of critical experiments benchmarks

International Nuclear Information System (INIS)

Durst, B.M.; Bierman, S.R.; Clayton, E.D.

1978-03-01

Data from critical experiments have been collected together for use as benchmarks in evaluating calculational techniques and nuclear data. These benchmarks have been selected from the numerous experiments performed on homogeneous plutonium systems. No attempt has been made to reproduce all of the data that exists. The primary objective in the collection of these data is to present representative experimental data defined in a concise, standardized format that can easily be translated into computer code input

Experiments on criticality carried out from 1975 till 1980

International Nuclear Information System (INIS)

Heinicke, W.; Tischer, A.; Weber, W.J.

1981-11-01

The report on hand includes the experiments on criticality published from 1975 till 1980. About 90 experiments with the most important related data are listed. They are capable of being called up, with the data base system KRITEXP, by 14 different descriptors or printed in any arrangement or order. This is the basis for a global or purposeful verification of the calculating method for criticality safety. The proof of reliability of the calculations for the criticality analysis are immediately relevant for the licencing procedure under atomic law for all plants of the nuclear fuel cycle where nuclear fuels are handled. Since no criticality experiments are being carried out in the Federal Republic of Germany, the data collection on hand will help to fill this gap with regard to the assessment of experiments carried out in other countries. (orig.) [de

Determination of the criticality parameters in heterogeneous Slab by the LTS{sub N} method

Energy Technology Data Exchange (ETDEWEB)

Borges, Volnei [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Dept. de Engenharia Nuclear; Derivi, Alexandre Guimaraes [Universidade Regional Integrada (URI), Erechim, RS (Brazil)

2001-07-01

The goal of this work consists in the use of the LTS{sub N} method in criticality problems. This method consists basically in the application of the Laplace Transform to a system of ordinary differential equations generated by the SN approach, resulting in a system of symbolic algebraic equations dependent on the complex parameters. After solving the algebraic system by means of the Schurr and diagonalization methods, the angular fluxes are obtained performing the inverse Laplace transform, which is carried out using the Heaviside formula. This methodology is used in determination of K{sub eff}, critical thickness and the atomic density for a heterogeneous planar slab. This procedure leads the solution of eigenvalue problem to the solution of a transcendental equation. Numerical results are reported. (author)

What’s so Critical about Critical Neuroscience? -Rethinking Experiment, Enacting Critique

Directory of Open Access Journals (Sweden)

Des eFitzgerald

2014-05-01

Full Text Available In the midst of on-going hype about the power and potency of the new brain sciences, scholars within ‘Critical Neuroscience’ have called for a more nuanced and sceptical neuroscientific knowledge-practice. Drawing especially on the Frankfurt School, they urge neuroscientists towards a more critical approach – one that re-inscribes the objects and practices of neuroscientific knowledge within webs of social, cultural, historical and political-economic contingency. This paper is an attempt to open up the black-box of ‘critique’ within Critical Neuroscience itself. Specifically, we argue that limiting enactments of critique to the invocation of context misses the force of what a highly-stylized and tightly-bound neuroscientific experiment can actually do. We show that, within the neuroscientific experiment itself, the world-excluding and context-denying ‘rules of the game’ may also enact critique, in novel and surprising forms, while remaining formally independent of the workings of society, and culture, and history. To demonstrate this possibility, we analyze the Optimally Interacting Minds paradigm, a neuroscientific experiment that used classical psychophysical methods to show that, in some situations, people worked better as a collective, and not as individuals – a claim that works precisely against reactionary tendencies that prioritise individual over collective agency, but that was generated and legitimized entirely within the formal, context-denying conventions of neuroscientific experimentation. At the heart of this paper is a claim that it was precisely the rigours and rules of the experimental game that allowed these scientists to enact some surprisingly critical, and even radical, gestures. We conclude by suggesting that, in the midst of large-scale neuroscientific initiatives, it may be 'experiment,' and not 'context,' that forms the meeting-ground between neuro-biological and socio-political research practices.

Flux-driven simulations of turbulence collapse

Energy Technology Data Exchange (ETDEWEB)

Park, G. Y.; Kim, S. S.; Jhang, Hogun; Rhee, T. [National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of); Diamond, P. H. [National Fusion Research Institute, Daejeon 305-333 (Korea, Republic of); CASS and Department of Physics, University of California, San Diego, La Jolla, California 92093-0429 (United States); Xu, X. Q. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)

2015-03-15

Using three-dimensional nonlinear simulations of tokamak turbulence, we show that an edge transport barrier (ETB) forms naturally once input power exceeds a threshold value. Profiles, turbulence-driven flows, and neoclassical coefficients are evolved self-consistently. A slow power ramp-up simulation shows that ETB transition is triggered by the turbulence-driven flows via an intermediate phase which involves coherent oscillation of turbulence intensity and E×B flow shear. A novel observation of the evolution is that the turbulence collapses and the ETB transition begins when R{sub T} > 1 at t = t{sub R} (R{sub T}: normalized Reynolds power), while the conventional transition criterion (ω{sub E×B}>γ{sub lin} where ω{sub E×B} denotes mean flow shear) is satisfied only after t = t{sub C} ( >t{sub R}), when the mean flow shear grows due to positive feedback.

Fabrication of visible-light-driven Ag/TiO{sub 2} heterojunction composites induced by shock wave

Energy Technology Data Exchange (ETDEWEB)

Xu, Chunxiao [School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); Chen, Pengwan, E-mail: pwchen@bit.edu.cn [School of Materials Science and Engineering, Beijing Institute of Technology, Beijing 100081 (China); State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081 (China); Liu, Jianjun [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Yin, Hao [Institute of Systems Engineering, China Academy of Engineering Physics, Mianyang 612900, Sichuan Province (China); Gao, Xin; Mei, Xiaofeng [State Key Laboratory of Explosion Science and Technology, Beijing Institute of Technology, Beijing 100081 (China)

2016-09-15

Using metatitanic acid (H{sub 2}TiO{sub 3}) and silver nitrate (AgNO{sub 3}) as titanium precursor and silver source respectively, a visible-light responsible Ag/TiO{sub 2} heterojunction photocatalyst is successfully prepared by shock wave with detonation-driven flyer impact. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV–visible diffuse reflectance spectroscopy (UV–Vis DRS) and photoluminescence (PL) emission spectra are employed to characterize the phase structure, morphology, chemical composition and optical property of the recovered samples. The results indicate the metatitanic acid transforms to pure rutile TiO{sub 2} phase by shock wave which possess large surface area. Ag nanoparticles cover on the surface of TiO{sub 2} uniformly and a nanojunction structure is formed efficiently, which play important roles as an electron-conduction bridge and in the surface plasmon resonance effect. Ag modification feasibly improves the separation efficiency for photoinduced electron–hole pairs and enhances the visible-light response. Furthermore, due to the further enhanced separation for photogenerated charges resulting from close interfacial contact of the hetero structure, the obtained Ag/TiO{sub 2} photocatalyst exhibit remarkably improved photocatalytic activities (88% within 2 h) than that of P25 and shock induced pure TiO{sub 2} for the degradation of Rhodamine B under simulated sunlight irradiation. The experimental result shows the shock loading is an effective method to get Ag/TiO{sub 2} photocatalyst and offers new ideas to fabricate other heterojunction composite materials. - Highlights: • Shock wave was a new method of material modification. • The Ag/TiO{sub 2} hetero structure was formed efficiently by shock loading. • The visible-light responsible sample showed an enhanced photocatalytic activity. • This work gave new ideas to fabricate other heterojunction materials.

Critical experiments analysis by ABBN-90 constant system

Energy Technology Data Exchange (ETDEWEB)

Tsiboulia, A.; Nikolaev, M.N.; Golubev, V. [Institute of Physics and Power Engineering, Obninsk (Russian Federation)] [and others

1997-06-01

The ABBN-90 is a new version of the well-known Russian group-constant system ABBN. Included constants were calculated based on files of evaluated nuclear data from the BROND-2, ENDF/B-VI, and JENDL-3 libraries. The ABBN-90 is intended for the calculation of different types of nuclear reactors and radiation shielding. Calculations of criticality safety and reactivity accidents are also provided by using this constant set. Validation of the ABBN-90 set was made by using a computerized bank of evaluated critical experiments. This bank includes the results of experiments conducted in Russia and abroad of compact spherical assemblies with different reflectors, fast critical assemblies, and fuel/water-solution criticalities. This report presents the results of the calculational analysis of the whole collection of critical experiments. All calculations were produced with the ABBN-90 group-constant system. Revealed discrepancies between experimental and calculational results and their possible reasons are discussed. The codes and archives INDECS system is also described. This system includes three computerized banks: LEMEX, which consists of evaluated experiments and their calculational results; LSENS, which consists of sensitivity coefficients; and LUND, which consists of group-constant covariance matrices. The INDECS system permits us to estimate the accuracy of neutronics calculations. A discussion of the reliability of such estimations is finally presented. 16 figs.

Observation of mesoscopic structure in NdBa sub 2 Cu sub 3 O sub 7 sub - subdelta by small-angle neutron scattering

CERN Document Server

Miyata, S; Suzuki, J I; Kuroda, K; Koshizuka, N

2003-01-01

In order to clarify the origin of the high critical current density (J sub c) of NdBa sub 2 Cu sub 3 O sub 7 sub - subdelta (Nd123), we investigated the inhomogeneities in this material by small-angle neutron scattering (SANS) experiments. As a result of numerical calculations, it was found that the anisotropic scattering patterns and radial intensity profiles can be explained by the existence of elliptic cylindrical objects of which the cylindrical axis is parallel to the crystallographic c-axis. Long and short elliptic axis lengths and the height of the elliptic cylinders in the high-J sub c sample are about 400, 200 and 100 nm, and those of the low-J sub c sample are about 200, 100 and 50 nm. Since these two samples have been heat-treated in different manners, it is suggested that sizes of the elliptic cylinders are affected by the heat treatments and this change in scale, as a result, increases or decreases the J sub c characteristics of the samples. (author)

Criticality experiments with fast flux test facility fuel pins

International Nuclear Information System (INIS)

Bierman, S.R.

1990-11-01

A United States Department of Energy program was initiated during the early seventies at the Hanford Critical Mass Laboratory to obtain experimental criticality data in support of the Liquid Metal Fast Breeder Reactor Program. The criticality experiments program was to provide basic physics data for clean well defined conditions expected to be encountered in the handling of plutonium-uranium fuel mixtures outside reactors. One task of this criticality experiments program was concerned with obtaining data on PuO 2 -UO 2 fuel rods containing 20--30 wt % plutonium. To obtain this data a series of experiments were performed over a period of about twelve years. The experimental data obtained during this time are summarized and the associated experimental assemblies are described. 8 refs., 7 figs

Jezebel: Reconstructing a Critical Experiment from 60 Years Ago

Energy Technology Data Exchange (ETDEWEB)

Favorite, Jeffrey A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-02-15

The Jezebel experiment of 1954-1955 was a very small, nearly-spherical, nearly-bare (unreflected), nearly-homogeneous assembly of plutonium alloyed with gallium. This experiment was used to determine the critical mass of spherical, bare, homogeneous Pu-alloy. In 1956, the critical mass of Pu-alloy was determined to be 16.45 ± 0.05 kg. The experiment was reevaluated in 1969 using logbooks from the 1950s and updated nuclear cross sections. The critical mass of Pu-alloy was determined to be 16.57 ± 0.10 kg. In 2013, the ²³⁹Pu Jezebel experiment was again reevaluated, this time using detailed geometry and materials models and modern nuclear cross sections in high-fidelity Monte Carlo neutron transport calculations. Documentation from the 1950s was often inconsistent or missing altogether, and assumptions had to be made. The critical mass of Pu-alloy was determined to be 16.624 ± 0.075 kg. Historic documents were subsequently found that validated some of the 2013 assumptions and invalidated others. In 2016, the newly found information was used to once again reevaluate the ²³⁹Pu Jezebel experiment. The critical mass of Pu-alloy was determined to be 16.624 ± 0.065 kg. This talk will discuss each of these evaluations, focusing on the calculation of the uncertainty as well as the critical mass. We call attention to the ambiguity, consternation, despair, and euphoria involved in reconstructing the historic Jezebel experiment. This talk is quite accessible for undergraduate students as well as non-majors.

Critical behavior of order-parameter fluctuations in liquid 4He near T/sub lambda/

International Nuclear Information System (INIS)

Lambert, B.; Perzynski, R.; Salin, D.

1979-01-01

We hve measured the critical attenuation of first sound in liquid 4 He from 550 to 1700 MHz. We can describe the attenuation due to the fluctuations of the order parameter up to 1.7 GHz, using experimental data at lower frequencies from various authors. Above T/sub lambda/, the fluctuations are the only phenomena and are analyzed with a scaling function of ωtau 2 with a characteristic time tau 2 = 2 x 10 -12 x t/sup -1.062/ sec, t = vertical-bar (T-T/sub lambda/)/T/sub lambda/vertical-bar. Below T/sub lambda/, several phenomena are present. In the range of 1 GHz, the main contribution is due to the fluctuations. We demonstrate experimentally that the fluctuation attenuation is not symmetric about T/sub lambda/. We fit our data with a scaling function of ωtau 2

Critical behavior of the three-dimensional Heisenberg antiferromagnet RbMnF<sub>3sub>

DEFF Research Database (Denmark)

Coldea, R.; Cowley, R.A.; Perring, T.G.

1998-01-01

component evolves below T-N into the longitudinal susceptibility identified in an earlier polarized neutron experiment. The intensity and energy width of the longitudinal scattering decrease on cooling below T-N. Down to the lowest temperatures where the longitudinal susceptibility could be measured......The magnetic critical scattering of the near-ideal three-dimensional Heisenberg antiferromagnet (AF) RbMnF3 has been remeasured using neutron scattering. The critical dynamics has been studied in detail in the temperature range 0.77T(N)

Recovery of Palm Oil and Valuable Material from Oil Palm Empty Fruit Bunch by Sub-critical Water.

Science.gov (United States)

Ahmad Kurnin, Nor Azrin; Shah Ismail, Mohd Halim; Yoshida, Hiroyuki; Izhar, Shamsul

2016-01-01

Oil palm empty fruit bunch (EFB) is one of the solid wastes produced in huge volume by palm oil mill. Whilst it still contains valuable oil, approximately 22.6 million tons is generated annually and treated as solid waste. In this work, sub-critical water (sub-cw) was used to extract oil, sugar and tar from spikelet of EFB. The spikelet was treated with sub-cw between 180-280°C and a reaction time of 2 and 5 minutes. The highest yield of oil was 0.075 g-oil/g-dry EFB, obtained at 240°C and reaction time of 5 minutes. Astonishingly, oil that was extracted through this method was 84.5% of that obtained through Soxhlet method using hexane. Yield of oil extracted was strongly affected by the reaction temperature and time. Higher reaction temperature induces the dielectric constant of water towards the non-polar properties of solvent; thus increases the oil extraction capability. Meanwhile, the highest yield of sugar was 0.20 g-sugar/g-dry EFB obtained at 220°C. At this temperature, the ion product of water is high enough to enable maximum sub-critical water hydrolysis reaction. This study showed that oil and other valuable material can be recovered using water at sub-critical condition, and most attractive without the use of harmful organic solvent.

Power reactors and sub-critical blanket systems with lead and lead-bismuth as coolant and/or target material. Utilization and transmutation of actinides and long lived fission products

International Nuclear Information System (INIS)

2003-05-01

High level radioactive waste disposal is an issue of great importance in the discussion of the sustainability of nuclear power generation. The main contributors to the high radioactivity are the fission products and the minor actinides. The long lived fission products and minor actinides set severe demands on the arrangements for safe waste disposal. Fast reactors and accelerator driven systems (ADS) are under development in Member States to reduce the long term hazard of spent fuel and radioactive waste, taking advantage of their incineration and transmutation capability. Important R and D programmes are being undertaken in many Member States to substantiate this option and advance the basic knowledge in this innovative area of nuclear energy development. The conceptual design of the lead cooled fast reactor concept BREST-OD-300, as well as various other conceptual designs of lead/lead-bismuth cooled fast reactors have been developed to meet enhanced safety and non-proliferation requirements, aiming at both energy production and transmutation of nuclear waste. Some R and D studies indicate that the use of lead and lead-bismuth coolant has some advantages in comparison with existing sodium cooled fast reactor systems, e.g.: simplified design of fast reactor core and BOP, enhanced inherent safety, and easier radwaste management in related fuel cycles. Moreover, various ADS conceptual designs with lead and lead-bismuth as target material and coolant also have been pursued. The results to date are encouraging, indicating that the ADS has the potential to offer an option for meeting the challenges of the back end fuel cycle. During the last decade, there have been substantial advances in several countries with their own R and D programme in the fields of lead/lead-bismuth cooled critical and sub-critical concepts. coolant technology, and experimental validation. In this context, international exchange of information and experience, as well as international

Parachors in terms of critical temperature, critical pressure and acentric factor

Energy Technology Data Exchange (ETDEWEB)

Broseta, D.; Ragil, K.

1995-12-31

The method of parachors is widely used in conventional thermodynamic codes and reservoir simulators to calculate oil/gas interfacial tensions of complex hydrocarbon mixtures. In the low-to-moderate interfacial tension regime, a value p{approx}11/3 has previously been shown to be the {open_quotes}best{close_quotes} parachor exponent. This exponent is a critical exponent and its value is consistent with the values of critical exponents characterizing the liquid/vapor critical behavior. Therefore parachors may be viewed as critical amplitudes. By using critical scaling theory, parachors are related to other critical amplitudes and critical parameters that describe the bulk thermodynamic behavior of fluids. A simple expression relating the parachor of a pure compound to its critical temperature T{sub c}, critical pressure P{sub c}, and acentric factor {omega} is proposed: P= (0.85-0.19{omega})T{sub c}{sup 12/11}/P{sub c}{sup 9/11} where the parachor P is in units of (dyn/cm){sup 3/11}cm{sup 3}/mol, T{sub c} in K and P{sub c} in MPa. This equation matches (within experimental error) the known parachor values of normal fluids (e.g. alkanes, aromatics, CO{sub 2}, N{sub 2}, H{sub 2}S, etc...).

Effect of hydrostatic pressure on magnetic and magnetocaloric properties in La{sub 0.35}Pr{sub 0.35}Ca{sub 0.3}MnO{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Thiyagarajan, R. [Centre for High Pressure Research, School of Physics, Bharathidasan University, Tiruchirapalli 620024, Tamil Nadu (India); Esakki Muthu, S. [Centre for High Pressure Research, School of Physics, Bharathidasan University, Tiruchirapalli 620024, Tamil Nadu (India); Univ. Grenoble Alpes and CEA, INAC-SPSMS, F-38000 Grenoble (France); Manikandan, K. [Centre for High Pressure Research, School of Physics, Bharathidasan University, Tiruchirapalli 620024, Tamil Nadu (India); Arumugam, S., E-mail: sarumugam1963@yahoo.com [Centre for High Pressure Research, School of Physics, Bharathidasan University, Tiruchirapalli 620024, Tamil Nadu (India)

2016-01-15

Magnetization of polycrystalline La{sub 0.35}Pr{sub 0.35}Ca{sub 0.3}MnO{sub 3} sample has been measured as a function of temperature (T) and magnetic field (H) under various external hydrostatic pressures (P) up to ~1 GPa. At ambient P, the sample exhibits paramagnetic (PM)–ferromagnetic (FM) transition (T{sub C}) at 167 K and 173 K in cooling and warming cycles respectively under the magnetic field (µ{sub 0}.H) of 0.1 T. It also shows a hysteresis during both temperature- and field- dependence of magnetization measurements at ambient P, suggests the presence of a first-order transition. Moreover, the field dependence of magnetization shows S type field-induced metamagnetic transition (FIMMT) over a temperature range below T{sub C} in the FM state. The application of P in M(T) increases T{sub C} at a rate [dT{sub C}/dP] of 13.9 K/GPa, but the thermally-driven first-order transition is not affected by P. However, the applied P suppresses FIMMT and reduces field-driven first-order transition in the magnetization isotherms [M(H)]below T{sub C}. H increases both magnetic entropy change (∆S{sub m}) and Relative Cooling Power (RCP), whereas the P slightly increases ∆S{sub m}{sup max} and no appreciable change in RCP. These results suggest that H and P can be used as a tool to enhance magnetocaloric values in the phase separated manganites. - Highlights: • At ambient P, La{sub 0.35}Pr{sub 0.35}Ca{sub 0.3}MnO{sub 3} sample shows first-order PM–FM transition. • P increases the T{sub C} at a rate of 13.9 K/GPa, thermal hysteresis is not affected. • P diminishes the field-driven first-order PM–FM transition, suppresses FIMMMT. • H increases ∆S{sub m} and RCP. P slightly increases ∆S{sub m}{sup max}, but no change in RCP by P.

Effects of Al{sub 2}O{sub 3} nanoparticles deposition on critical heat flux of R-123 in flow boiling heat transfer

Energy Technology Data Exchange (ETDEWEB)

Seo, Seok Bin; Bang, In Cheol [School of Mechanical and Nuclear Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan (Korea, Republic of)

2015-06-15

In this study, R-123 flow boiling experiments were carried out to investigate the effects of nanoparticle deposition on heater surfaces on flow critical heat flux (CHF) and boiling heat transfer. It is known that CHF enhancement by nanoparticles results from porous structures that are very similar to layers of Chalk River unidentified deposit formed on nuclear fuel rod surfaces during the reactor operation period. Although previous studies have investigated the surface effects through surface modifications, most studies are limited to pool boiling conditions, and therefore, the effects of porous surfaces on flow boiling heat transfer are still unclear. In addition, there have been only few reports on suppression of wetting for decoupled approaches of reasoning. In this study, bare and Al{sub 2}O{sub 3} nanoparticle-coated surfaces were prepared for the study experiments. The CHF of each surface was measured with different mass fluxes of 1,600 kg/m{sup 2}s, 1,800 kg/m{sup 2}s, 2,100 kg/m{sup 2}s, 2,400 kg/m{sup 2}s, and 2,600 kg/m{sup 2}s. The nanoparticle-coated tube showed CHF enhancement up to 17% at a mass flux of 2,400 kg/m{sup 2}s compared with the bare tube. The factors for CHF enhancement are related to the enhanced rewetting process derived from capillary action through porous structures built-up by nanoparticles while suppressing relative wettability effects between two sample surfaces as a highly wettable R-123 refrigerant was used as a working fluid.

Providing Nuclear Criticality Safety Analysis Education through Benchmark Experiment Evaluation

International Nuclear Information System (INIS)

Bess, John D.; Briggs, J. Blair; Nigg, David W.

2009-01-01

One of the challenges that today's new workforce of nuclear criticality safety engineers face is the opportunity to provide assessment of nuclear systems and establish safety guidelines without having received significant experience or hands-on training prior to graduation. Participation in the International Criticality Safety Benchmark Evaluation Project (ICSBEP) and/or the International Reactor Physics Experiment Evaluation Project (IRPhEP) provides students and young professionals the opportunity to gain experience and enhance critical engineering skills.

Controllable synthesis of p-type Cu{sub 2}S nanowires for self-driven NIR photodetector application

Energy Technology Data Exchange (ETDEWEB)

Wu, Chun-Yan, E-mail: cywu@hfut.edu.cn; Pan, Zhi-Qiang; Liu, Zhu; Wang, You-Yi [Hefei University of Technology, School of Electronic Science and Applied Physics (China); Liang, Feng-Xia [Hefei University of Technology, School of Materials Science and Engineering and Anhui Provincial Key Laboratory of Advanced Functional Materials and Devices (China); Yu, Yong-Qiang; Wang, Li; Luo, Lin-Bao, E-mail: luolb@hfut.edu.cn [Hefei University of Technology, School of Electronic Science and Applied Physics (China)

2017-02-15

Face-centered cubic Cu{sub 2}S nanowires with length of up to 50 μm and diameters in the range of 100–500 nm are synthesized on Si substrates through the chemical vapor deposition method using a mixed gas of Ar and H{sub 2} as the carrier gas under a chamber pressure of about 700 Torr. It was found that the growth of quasi 1D nanostructure followed a typical vapor-liquid-solid (VLS) mechanism in which the element Cu was reduced by H{sub 2} as the catalyst. The as-synthesized Cu{sub 2}S nanowires exhibited typical p-type semiconducting characteristics with a conductivity of about 600 S cm{sup −1} and a hole mobility (μ{sub h}) of about 72 cm{sup 2} V{sup −1} s{sup −1}. Further study reveals that p-Cu{sub 2}S nanowires/n-Si heterojunction exhibits distinct rectifying characteristics with a turn-on voltage of ~0.6 V and a rectification ratio of ~300 at ±1 V in the dark and a pronounced photovoltaic behavior with an open circuit voltage (V{sub oc}) of 0.09 V and a short circuit current (I{sub sc}) of 65 nA when illuminated by the NIR light (790 nm, 0.35 mW cm{sup −1}), giving rise to a responsivity (R) about 0.8 mA W{sup −1} and specific detectivity (D*) 6.7 × 10{sup 10} cm Hz{sup 1/2} W{sup −1} at zero bias, which suggests the potential of as-synthesized Cu{sub 2}S nanowires applied in the field of self-driven NIR photodetector.

Atrial fibrillation driven by micro-anatomic intramural re-entry revealed by simultaneous sub-epicardial and sub-endocardial optical mapping in explanted human hearts.

Science.gov (United States)

Hansen, Brian J; Zhao, Jichao; Csepe, Thomas A; Moore, Brandon T; Li, Ning; Jayne, Laura A; Kalyanasundaram, Anuradha; Lim, Praise; Bratasz, Anna; Powell, Kimerly A; Simonetti, Orlando P; Higgins, Robert S D; Kilic, Ahmet; Mohler, Peter J; Janssen, Paul M L; Weiss, Raul; Hummel, John D; Fedorov, Vadim V

2015-09-14

The complex architecture of the human atria may create physical substrates for sustained re-entry to drive atrial fibrillation (AF). The existence of sustained, anatomically defined AF drivers in humans has been challenged partly due to the lack of simultaneous endocardial-epicardial (Endo-Epi) mapping coupled with high-resolution 3D structural imaging. Coronary-perfused human right atria from explanted diseased hearts (n = 8, 43-72 years old) were optically mapped simultaneously by three high-resolution CMOS cameras (two aligned Endo-Epi views (330 µm2 resolution) and one panoramic view). 3D gadolinium-enhanced magnetic resonance imaging (GE-MRI, 80 µm3 resolution) revealed the atrial wall structure varied in thickness (1.0 ± 0.7-6.8 ± 2.4 mm), transmural fiber angle differences, and interstitial fibrosis causing transmural activation delay from 23 ± 11 to 43 ± 22 ms at increased pacing rates. Sustained AF (>90 min) was induced by burst pacing during pinacidil (30-100 µM) perfusion. Dual-sided sub-Endo-sub-Epi optical mapping revealed that AF was driven by spatially and temporally stable intramural re-entry with 107 ± 50 ms cycle length and transmural activation delay of 67 ± 31 ms. Intramural re-entrant drivers were captured primarily by sub-Endo mapping, while sub-Epi mapping visualized re-entry or 'breakthrough' patterns. Re-entrant drivers were anchored on 3D micro-anatomic tracks (15.4 ± 2.2 × 6.0 ± 2.3 mm2, 2.9 ± 0.9 mm depth) formed by atrial musculature characterized by increased transmural fiber angle differences and interstitial fibrosis. Targeted radiofrequency ablation of the tracks verified these re-entries as drivers of AF. Integrated 3D structural-functional mapping of diseased human right atria ex vivo revealed that the complex atrial microstructure caused significant differences between Endo vs. Epi activation during pacing and sustained AF driven by intramural re-entry anchored to fibrosis-insulated atrial bundles. Published on

Study of critical beta non-circular tokamak equilibria sustained in steady state by beam driven currents

International Nuclear Information System (INIS)

Okano, K.; Ogawa, Y.; Naitou, H.

1988-07-01

A new MHD-equilibrium/current-drive analysis code was developed to analyse the high beta tokamak equilibria consistent with the beam driven current profiles. In this new code, the critical beta equilibrium, which is stable against the ballooning mode, the kink mode and the Mercier mode, is determined first using MHD equilibrium and stability analysis codes (EQLAUS/ERATO). Then, the current drive parameters and the plasma parameters, required to sustain this critical beta equilibrium, are determined by iterative calculations. The beam driven current profiles are evaluated by the Fokker-Planck calculations on individual flux surfaces, where the toroidal effects on the beam ion and plasma electron trajectories are considered. The pressure calculation takes into account the beam ion and fast alpha components. A peculiarity of our new method is that the obtained solution is not only consistent with the MHD equilibrium but also consistent with the critical beta limit conditions, in the current profile and the pressure profile. Using this new method, β ∼ 21 % bean and β ∼ 6 % D-type critical beta equilibria were scanned for various parameters; the major radius, magnetic field, temperature, injection energy, etc. It was found that the achievable Q value for the bean type was always about 30 % larger than for the D-type cases, where Q = fusion power/beam power. With strong beanness, Q ∼ 6 for DEMO type tokamaks (∼500 MWth) and Q ∼ 20 for power reactor size (4.5 GWth) are achievable. On the other hand, the Q value would not exceed sixteen for the D-type machines. (author)

Maternity health care: The experiences of Sub-Saharan African women in Sub-Saharan Africa and Australia.

Science.gov (United States)

Mohale, Hlengiwe; Sweet, Linda; Graham, Kristen

2017-08-01

Increasing global migration is resulting in a culturally diverse population in the receiving countries. In Australia, it is estimated that at least four thousand Sub-Saharan African women give birth each year. To respond appropriately to the needs of these women, it is important to understand their experiences of maternity care. The study aimed to examine the maternity experiences of Sub-Saharan African women who had given birth in both Sub-Saharan Africa and in Australia. Using a qualitative approach, 14 semi-structured interviews with Sub-Saharan African women now living in Australia were conducted. Data was analysed using Braun and Clark's approach to thematic analysis. Four themes were identified; access to services including health education; birth environment and support; pain management; and perceptions of care. The participants experienced issues with access to maternity care whether they were located in Sub-Saharan Africa or Australia. The study draws on an existing conceptual framework on access to care to discuss the findings on how these women experienced maternity care. The study provides an understanding of Sub-Saharan African women's experiences of maternity care across countries. The findings indicate that these women have maternity health needs shaped by their sociocultural norms and beliefs related to pregnancy and childbirth. It is therefore arguable that enhancing maternity care can be achieved by improving women's health literacy through health education, having an affordable health care system, providing respectful and high quality midwifery care, using effective communication, and showing cultural sensitivity including family support for labouring women. Copyright © 2016 Australian College of Midwives. Published by Elsevier Ltd. All rights reserved.

Subcritical Multiplication Parameters of the Accelerator-Driven System with 100 MeV Protons at the Kyoto University Critical Assembly

Directory of Open Access Journals (Sweden)

Jae-Yong Lim

2012-01-01

Full Text Available Basic experiments on the accelerator-driven system (ADS at the Kyoto University Critical Assembly are carried out by combining a solid-moderated and -reflected core with the fixed-field alternating gradient accelerator. The reaction rates are measured by the foil activation method to obtain the subcritical multiplication parameters. The numerical calculations are conducted with the use of MCNPX and JENDL/HE-2007 to evaluate the reaction rates of activation foils set in the core region and at the location of the target. Here, a comparison between the measured and calculated eigenvalues reveals a relative difference of around 10% in C/E values. A special mention is made of the fact that the reaction rate analyses in the subcritical systems demonstrate apparently the actual effect of moving the tungsten target into the core on neutron multiplication. A series of further ADS experiments with 100 MeV protons needs to be carried out to evaluate the accuracy of subcritical multiplication parameters.

Synthesis and characterization of highly efficient and stable Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt ternary hybrid structure

Energy Technology Data Exchange (ETDEWEB)

Deng, Jiatao; Liu, Lin; Niu, Tongjun; Sun, Xiaosong, E-mail: sunxs@scu.edu.cn

2017-05-01

Highlights: • Visible-light-driven Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt photocatalysts were prepared. • Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt showed highly efficient and stable photocatalystic activity. • The photocatalytic mechanism of Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt composite was given. - Abstract: Ag{sub 3}PO{sub 4} is an excellent photocatalyst with high efficiency and quantum yield, but suffers from the fast recombination of photogenerated electron-hole pairs and photo-corrosion. Hereby, the highly efficient and stable visible-light-driven Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt photocatalyst were prepared via a three-step wet chemical approach. The as-prepared Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt composite was characterized by X-ray diffraction, US-vis diffuse reflectance spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, photoluminescence spectra and transient photocurrent as well. Comparing with single Pr{sub 6}O{sub 11} or Ag{sub 3}PO{sub 4}, the prepared Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt composite exhibited much higher photocatalytic activity and stability for the degradation of Rhodamine B under visible light irradiation (>420 nm). The enhanced photocatalytic performance of Pr{sub 6}O{sub 11}/Ag{sub 3}PO{sub 4}/Pt composite has been attributed to the efficient separation of photo-generated electron-hole pairs through a scheme system composed of Pr{sub 6}O{sub 11,} Ag{sub 3}PO{sub 4} and Pt.

Final Report: Archiving Data to Support Data Synthesis of DOE Sponsored Elevated CO<sub>2sub> Experiments

Energy Technology Data Exchange (ETDEWEB)

Megonigal, James [Smithsonian Environmental Research Center, Edgewater, MD (United States); Lu, Meng [Smithsonian Environmental Research Center, Edgewater, MD (United States)

2017-09-05

Over the last three decades DOE made a large investment in field-scale experiments in order to understand the role of terrestrial ecosystems in the global carbon cycle, and forecast how carbon cycling will change over the next century. The Smithsonian Environmental Research Center received one of the first awards in this program and managed two long-term studies (25 years and 10 years) with a total of approximately $10 million of support from DOE, and many more millions leveraged from the Smithsonian Institution and agencies such as NSF. The present DOE grant was based on the premise that such a large investment demands a proper synthesis effort so that the full potential of these experiments are realized through data analysis and modeling. The goal of the this grant was to archive legacy data from two major elevated carbon dioxide experiments in DOE databases, and to engage in synthesis activities using these data. Both goals were met. All datasets deemed a high priority for data synthesis and modeling were prepared for archiving and analysis. Many of these datasets were deposited in DOE’s CDIAC, while others are being held at the Oak Ridge National Lab and the Smithsonian Institution until they can be received by DOE’s new ESS-DIVE system at Berkeley Lab. Most of the effort was invested in researching and re-constituting high-quality data sets from a 30-year elevated CO<sub>2sub> experiment. Using these data, the grant produced products that are already benefiting climate change science, including the publication of new coastal wetland allometry equations based on 9,771 observations, public posting of dozens of datasets, metadata and supporting codes from long-term experiments at the Global Change Research Wetland, and publication of two synthetic data papers on scrub oak forest responses to elevated CO<sub>2sub>. In addition, three papers are in review or nearing submission reporting unexpected long-term patterns in ecosystem responses to elevated CO<sub

Supercurrents in HgBa{sub 2}CaCu{sub 2}O{sub 6+{delta}} and TlBa{sub 2}CaCu{sub 2}O{sub 7} epitaxial thin films

Energy Technology Data Exchange (ETDEWEB)

Gapud, A.A.; Wu, J.Z.; Fang, L.; Yan, S.L.; Xie, Y.Y. [Department of Physics and Astronomy, University of Kansas, Lawrence, Kansas 66045-2151 (United States); Siegal, M.P.; Overmyer, D.L. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)

1999-06-01

The availability of high-quality epitaxial thin films of HgBa{sub 2}CaCu{sub 2}O{sub 6+{delta}} (Hg-1212) and TlBa{sub 2}CaCu{sub 2}O{sub 7} (Tl-1212) with high critical current densities (J{sub c}) has made it possible to examine and compare the J{sub c} of these species. Results reveal that the J{sub c} of 1212 species have very similar temperature behavior at low fields, strongly suggesting that the 30 K shift in critical temperature (T{sub c}) induced by the exchange of Hg and Tl in the 1212 structure is due largely to a change in charge carrier density and/or electronic band structure. {copyright} {ital 1999 American Institute of Physics.}

Theory of ion-temperature-gradient-driven turbulence in tokamaks

International Nuclear Information System (INIS)

Lee, G.S.; Diamond, P.H.

1986-01-01

An analytic theory of ion-temperature-gradient-driven turbulence in tokamaks is presented. Energy-conserving, renormalized spectrum equations are derived and solved in order to obtain the spectra of stationary ion-temperature-gradient-driven turbulence. Corrections to mixing-length estimates are calculated explicitly. The resulting anomalous ion thermal diffusivity chi/sub i/ = 0.4[(π/2)ln(1 + eta/sub i/)] 2 [(1 + eta/sub i/)/tau] 2 rho/sub s/ 2 c/sub s//L/sub s/ is derived and is found to be consistent with experimentally-deduced thermal diffusivities. The associated electron thermal diffusivity and particle and heat-pinch velocities are also calculated. The effect of impurity gradients on saturated ion-temperature-gradient-driven turbulence is discussed and a related explanation of density profile steepening during Z-mode operation is proposed. 35 refs., 4 figs

Electrostatically Driven Nanoballoon Actuator.

Science.gov (United States)

Barzegar, Hamid Reza; Yan, Aiming; Coh, Sinisa; Gracia-Espino, Eduardo; Dunn, Gabriel; Wågberg, Thomas; Louie, Steven G; Cohen, Marvin L; Zettl, Alex

2016-11-09

We demonstrate an inflatable nanoballoon actuator based on geometrical transitions between the inflated (cylindrical) and collapsed (flattened) forms of a carbon nanotube. In situ transmission electron microscopy experiments employing a nanoelectromechanical manipulator show that a collapsed carbon nanotube can be reinflated by electrically charging the nanotube, thus realizing an electrostatically driven nanoballoon actuator. We find that the tube actuator can be reliably cycled with only modest control voltages (few volts) with no apparent wear or fatigue. A complementary theoretical analysis identifies critical parameters for nanotube nanoballoon actuation.

Fast critical experiments in FCA and their analysis

International Nuclear Information System (INIS)

Hirota, Jitsuya

1984-02-01

JAERI Fast Critical Facility FCA went critical for the first time in April, 1967. Since then, critical experiments and their analysis were carried out on thirty-five assemblies until march, 1982. This report summarizes many achievements obtained in these fifteen years and points out disagreements observed between the calculation and experiment for further studies. A series of mock-up experiments for Experimental Fast Reactor JOYO, a theoretical and numerical study of adjustment of group constants by using integral data and a development of proton-recoil counter system for fast neutron spectrum measurement won high praise. Studies of Doppler effect of structural materials, effect of fission product accumulation on sodium-void worth, axially heterogeneous core and actinide cross sections attracted world-side attention. Significant contributions were also made to Prototype Fast Breeder Reactor MONJU through the partial mock-up experiments. Disagreements between the calculation and experiment were observed in the following items; reaction rate distribution and reactivity worth of B 4 C absorber in radial blanket, central reactivity worth in core with reflector, plate/pin fuel heterogeneity effect on criticality, sodium-void effect in central core region, Doppler effect of structural materials, core neutron spectrum near large resonances of iron and oxygen, effect of fission product accumulation on sodium-void worth, physics property of heterogeneous core, reactivity change resulted from fuel slumping and so on. Further efforts should be made to solve these disagreements through recalculating the experimental results with newly developed data and methods and carrying out the experiments intended to identify the cause of disagreement. (author)

Visible-light-driven g-C{sub 3}N{sub 4}/Ti{sup 3+}-TiO{sub 2} photocatalyst co-exposed {0 0 1} and {1 0 1} facets and its enhanced photocatalytic activities for organic pollutant degradation and Cr(VI) reduction

Energy Technology Data Exchange (ETDEWEB)

Lu, Dan; Zhang, Gaoke, E-mail: gkzhang@whut.edu.cn; Wan, Zhen

2015-12-15

Graphical abstract: Schematic illustration for the mechanism of photo-generated charge carrier transfers in g-C{sub 3}N{sub 4}/Ti{sup 3+}-TiO{sub 2} photocatalyst and its visible-light photocatalytic performance. - Highlights: • g-C{sub 3}N{sub 4}/Ti{sup 3+}-TiO{sub 2} composite co-exposed {0 0 1} and {1 0 1} facets of TiO{sub 2} was synthesized. • RhB and Cr(VI) aqueous solutions were used to evaluate the photocatalytic activities. • h{sup +} and ·O{sub 2}{sup −} are the critical reactive species in the degradation of RhB solution. • Surface heterojunction of co-exposed {1 0 1} and {0 0 1} facets improve the separation. - Abstract: Novel g-C{sub 3}N{sub 4/}Ti{sup 3+}-TiO{sub 2} photocatalyst co-exposed {0 0 1} and {1 0 1} facets of TiO{sub 2} was synthesized via a hydrothermal–sonication assisted strategy. The photocatalytic activities of the as-obtained photocatalyst were evaluated by the degradation of rhodamine B (RhB) and the reduction of Cr(VI) under visible-light irradiation. It was found that the g-C{sub 3}N{sub 4}/Ti{sup 3+}-TiO{sub 2} composites with 6 wt% g-C{sub 3}N{sub 4} exhibited the highest visible-light photocatalytic efficiency, which is also higher than the pure g-C{sub 3}N{sub 4} and Ti{sup 3+}-TiO{sub 2}. A possible photocatalytic mechanism was discussed on the basis of the theoretical analyses and scavenger experiments. Results show that holes (h{sup +}) and superoxide anions (·O{sub 2}{sup −}) reactive species participated in the degradation of RhB solution over the g-C{sub 3}N{sub 4}/Ti{sup 3+}-TiO{sub 2} composites. The enhanced photocatalytic activities of g-C{sub 3}N{sub 4}/Ti{sup 3+}-TiO{sub 2} composites can be attributed to the wide optical adsorption of g-C{sub 3}N{sub 4} and Ti{sup 3+} as well as the effectively separation and transportation of photo-generated electrons and holes pairs, which was resulted from the surface heterojunction between the g-C{sub 3}N{sub 4} and Ti{sup 3+}-TiO{sub 2} nanosheets co-exposed {1

Building and managing strategic alliances in technology-driven start-ups: a critical review of literature

OpenAIRE

Comi, Alice; Eppler, Martin J.

2009-01-01

In this article, we critically review the current literature on alliance formation and management with a particular emphasis on small businesses, and on managerial implications for start-up enterprises. In the beginning of the article, we discuss the advantages and the challenges of inter-organizational collaboration, by taking the perspective of technology-driven start-ups operating in highly competitive environments. We then review the managerial advice suggested by the current liter...

252Cf-source-driven neutron noise analysis method

International Nuclear Information System (INIS)

Mihalczo, J.T.; King, W.T.; Blakeman, E.D.

1985-01-01

The 252 Cf-source-driven neutron noise analysis method has been tested in a wide variety of experiments that have indicated the broad range of applicability of the method. The neutron multiplication factor k/sub eff/ has been satisfactorily detemined for a variety of materials including uranium metal, light water reactor fuel pins, fissile solutions, fuel plates in water, and interacting cylinders. For a uranyl nitrate solution tank which is typical of a fuel processing or reprocessing plant, the k/sub eff/ values were satisfactorily determined for values between 0.92 and 0.5 using a simple point kinetics interpretation of the experimental data. The short measurement times, in several cases as low as 1 min, have shown that the development of this method can lead to a practical subcriticality monitor for many in-plant applications. The further development of the method will require experiments oriented toward particular applications including dynamic experiments and the development of theoretical methods to predict the experimental observables

Laser driven shock wave experiments for equation of state studies at megabar pressures

CERN Document Server

Pant, H C; Senecha, V K; Bandyopadhyay, S; Rai, V N; Khare, P; Bhat, R K; Gupta, N K; Godwal, B K

2002-01-01

We present the results from laser driven shock wave experiments for equation of state (EOS) studies of gold metal. An Nd:YAG laser chain (2 J, 1.06 mu m wavelength, 200 ps pulse FWHM) is used to generate shocks in planar Al foils and Al + Au layered targets. The EOS of gold in the pressure range of 9-13 Mbar is obtained using the impedance matching technique. The numerical simulations performed using the one-dimensional radiation hydrodynamic code support the experimental results. The present experimental data show remarkable agreement with the existing standard EOS models and with other experimental data obtained independently using laser driven shock wave experiments.

Laser driven shock wave experiments for equation of state studies at megabar pressures

International Nuclear Information System (INIS)

Pant, H C; Shukla, M; Senecha, V K; Bandyopadhyay, S; Rai, V N; Khare, P; Bhat, R K; Gupta, N K; Godwal, B K

2002-01-01

We present the results from laser driven shock wave experiments for equation of state (EOS) studies of gold metal. An Nd:YAG laser chain (2 J, 1.06 μm wavelength, 200 ps pulse FWHM) is used to generate shocks in planar Al foils and Al + Au layered targets. The EOS of gold in the pressure range of 9-13 Mbar is obtained using the impedance matching technique. The numerical simulations performed using the one-dimensional radiation hydrodynamic code support the experimental results. The present experimental data show remarkable agreement with the existing standard EOS models and with other experimental data obtained independently using laser driven shock wave experiments

Characterization of Si sub 1 sub - sub x Ge sub x thin films prepared by sputtering

CERN Document Server

Noguchi, T

2000-01-01

By bombarding solid targets, we deposited Si sub 1 sub - sub x Ge sub x thin films by sputtering without using inflammable CVD (chemical vapor deposition) gases. After the B sup + -implanted Si sub 1 sub - sub x Ge sub x films were thermally annealed, they were characterized. As the content of Ge increased, the refractive index increased and the band edge narrowed. The higher the annealing temperature, the lower the resistivity. For Si sub 1 sub - sub x Ge sub x films with a high Ge content (X approx 0.5), the flat-band voltage of the gate deduced from C-V curve was adjusted to the middle point between p sup + and n sup + polySi gates. Boron-doped SiGe films are promising gate materials for MOS (metal oxide semiconductor) and SOI (silicon on insulator) transistors driven at low driving voltage.

Introduction to 'International Handbook of Criticality Safety Benchmark Experiments'

International Nuclear Information System (INIS)

Komuro, Yuichi

1998-01-01

The Criticality Safety Benchmark Evaluation Project (CSBEP) was initiated in 1992 by the United States Department of Energy. The project quickly became an international effort as scientists from other interested countries became involved. The International Criticality Safety Benchmark Evaluation Project (ICSBEP) is now an official activity of the Organization for Economic Cooperation and Development-Nuclear Energy Agency (OECD-NEA). 'International Handbook of Criticality Safety Benchmark Experiments' was prepared and is updated year by year by the working group of the project. This handbook contains criticality safety benchmark specifications that have been derived from experiments that were performed at various nuclear critical facilities around the world. The benchmark specifications are intended for use by criticality safety engineers to validate calculation techniques used. The author briefly introduces the informative handbook and would like to encourage Japanese engineers who are in charge of nuclear criticality safety to use the handbook. (author)

Analysis of Fresh Fuel Critical Experiments Appropriate for Burnup Credit Validation

International Nuclear Information System (INIS)

DeHart, M.D.

1995-01-01

The ANS/ANS-8.1 standard requires that calculational methods used in determining criticality safety limits for applications outside reactors be validated by comparison with appropriate critical experiments. This report provides a detailed description of 34 fresh fuel critical experiments and their analyses using the SCALE-4.2 code system and the 27-group ENDF/B-IV cross-section library. The 34 critical experiments were selected based on geometry, material, and neutron interaction characteristics that are applicable to a transportation cask loaded with pressurized-water-reactor spent fuel. These 34 experiments are a representative subset of a much larger data base of low-enriched uranium and mixed-oxide critical experiments. A statistical approach is described and used to obtain an estimate of the bias and uncertainty in the calculational methods and to predict a confidence limit for a calculated neutron multiplication factor. The SCALE-4.2 results for a superset of approximately 100 criticals are included in uncertainty analyses, but descriptions of the individual criticals are not included

Two-dimensional TiO{sub 2}-based nanosheets co-modified by surface-enriched carbon dots and Gd{sub 2}O{sub 3} nanoparticles for efficient visible-light-driven photocatalysis

Energy Technology Data Exchange (ETDEWEB)

Lu, Dingze, E-mail: 1005116870@qq.com [Department of Physics and Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Wuhan University, Wuhan 430072 (China); Fang, Pengfei, E-mail: fangpf@whu.edu.cn [Department of Physics and Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Wuhan University, Wuhan 430072 (China); Ding, Junqian, E-mail: 630736958@qq.com [Department of Physics and Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Wuhan University, Wuhan 430072 (China); Yang, Minchen, E-mail: 1023635028@qq.com [Department of Physics and Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Wuhan University, Wuhan 430072 (China); Cao, Yufei, E-mail: 344541464@qq.com [Department of Physics and Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Wuhan University, Wuhan 430072 (China); Zhou, Yawei, E-mail: 769107311@qq.com [Department of Physics and Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Wuhan University, Wuhan 430072 (China); Peng, Kui, E-mail: 758007737@qq.com [Department of Physics and Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Wuhan University, Wuhan 430072 (China); Kondamareddy, Kiran Kumar, E-mail: kokila_kkk@yahoo.co.in [Department of Physics and Key Laboratory of Artificial Micro- and Nano-Structures of Ministry of Education, Wuhan University, Wuhan 430072 (China); Liu, Min, E-mail: liumhb@126.com [State Grid Zhejiang Electric Power Research Institute, Hangzhou, Zhejiang 310007 (China)

2017-02-28

Highlights: • Gd-C-TNSs with high stability and recycle usability were prepared by two-pot method. • Gd{sub 2}O{sub 3} loading results in the structure changes of TNSs and increase of the Ti{sup 3+} ions. • Modified CDs leads to obvious increase of optical absorption ability and red shift. • Appropriate amount of Gd{sub 2}O{sub 3} nanoparticles and CDs improve the separation of charges. • Gd-C-TNSs exhibit excellent synergistic photocatalytic activity for Cr(VI) and RhB. - Abstract: Two-dimensional TiO{sub 2}-based nanosheets (TNSs) co-modified by surface-enriched carbon dots (CDs) and Gd{sub 2}O{sub 3} nanoparticles: (Gd-C-TNSs), capable of exhibiting visible-light-driven photo catalysis were synthesized using a two-pot hydrothermal route. The samples had a sheet-like structure, thickness of approximately 3.6 nm, large specific surface area of 240–350 cm{sup 2}/g. The CDs (2–3 nm) and Gd{sub 2}O{sub 3} nanoparticles (1–2 nm) were highly dispersed over the surface of the nanosheets. The co-modification by Gd{sub 2}O{sub 3} nanoparticles and CDs influenced the crystallinity, crystal structure, and surface area of the TNSs, and improved the visible-light absorption. Surface photocurrent and fluorescence spectral studies revealed that the photo-generated charge carrier separation efficiency could be improved by an appropriate amount of modification. A very high efficiency was obtained using 0.5 at% Gd/Ti and 3.0 g/L of CDs. The visible-light-induced photocatalytic activity is enhanced under the isolated Cr(VI) system, isolated Rhodamin B (RhB) system, and the synergism between RhB degradation and Cr(VI) reduction for the Gd-C-TNSs photocatalysts. Initially, the photocatalytic activity gradually increased with an increase in the amount of CDs, and then decreased after attaining a maximum, in the case where 0.5 at% Gd/Ti and 3.0 g/L of CDs were used. The enhancement in the photocatalytic activity was attributed to the synergetic effect of the Gd{sub 2}O{sub

252Cf-source-driven neutron noise measurements of subcriticality for a slab tank containing aqueous Pu-U nitrate

International Nuclear Information System (INIS)

Mihalczo, J.T.; Blakeman, E.D.; Ragan, G.E.; Kryter, R.C.; Robinson, R.C.; Seino, H.

1987-08-01

In order to study nuclear criticality safety related to the development of fast breeder technology, 252 Cf-source-driven neutron noise analysis measurements were performed with a Pu-U nitrate solution in a slab tank of various heights and thickness varying 11.43 cm to 19.05 cm. The results and conclusions of these experiments are (1) a capability to measure the subcriticality of a multiplying system of slab geometry to a k/sub eff/ as low as 0.7 was demonstrated, (2) calculated neutron multiplication factors agreed with those from the experiments within ∼0.02, and (3) the applicability of the method for plutonium solution systems was demonstrated. This paper describes measurements in which the height of the slab was varied for a fixed thickness and the thickness varied for a fixed height, which are the first applications of this measurement method to slab geometry

The I{sub c}(H)-T{sub c}(H) phase boundary of superconducting Nb thin films with periodic and quasiperiodic antidot arrays

Energy Technology Data Exchange (ETDEWEB)

Bothner, D.; Kemmler, M.; Cozma, R.; Kleiner, R.; Koelle, D. [Physikalisches Institut and Center for Collective Quantum Phenomena, Universitaet Tuebingen (Germany); Misko, V.; Peeters, F. [Departement Fysica, Universiteit Antwerpen (Belgium); Nori, F. [Advanced Science Institute, RIKEN (Japan)

2011-07-01

The magnetic field dependent critical current I{sub c}(H) of superconducting thin films with artificial defects strongly depends on the symmetry of the defect arrangement. Likewise the critical temperature T{sub c}(H) of superconducting wire networks is heavily influenced by the symmetry of the system. Here we present experimental data on the I{sub c}(H)-T{sub c}(H) phase boundary of Nb thin films with artificial defect lattices of different symmetries. For this purpose we fabricated 60 nm thick Nb films with antidots in periodic (triangular) and five different quasiperiodic arrangements. The parameters of the antidot arrays were varied to investigate the influence of antidot diameter and array density. Experiments were performed with high temperature stability ({delta}T<1 mK) at 0.5{<=}T/T{sub c}{<=}1. From the I-V-characteristics at variable H and T we extract I{sub c}(H) and T{sub c}(H) for different voltage and resistance criteria. The experimental data for the critical current density are compared with results from numerical molecular dynamics simulations.

Spin dynamics in the high-field phase of quantum-critical S =1/2 TlCuCl sub 3

CERN Document Server

Rueegg, C; Furrer, A; Krämer, K; Güdel, H U; Vorderwisch, P; Mutka, H

2002-01-01

An external magnetic field suppresses the spin-energy gap in singlet ground state S=1/2 TlCuCl sub 3. The system becomes quantum-critical at H sub c approx 5.7 T, where the energy of the lowest Zeeman-split triplet excitation crosses the nonmagnetic ground state. Antiferromagnetic ordering is reported above H sub c , which underlines the three-dimensional nature of the observed quantum phase transition. The intrinsic parameters of S=1/2 TlCuCl sub 3 allow us to access the critical region microscopically by neutron scattering. A substantial study of the spin dynamics in the high-field phase of TlCuCl sub 3 at T=1.5 K up to H=12 T was performed for the first time. The results possibly indicate two dynamical regimes, which can be understood within characteristically renormalized triplet modes and a low-lying dynamics of potentially collective origin. (orig.)

Critical behavior of Y-doped Nd{sub 0.7}Sr{sub 0.3}MnO{sub 3} manganites exhibiting the tricritical point and large magnetocaloric effect

Energy Technology Data Exchange (ETDEWEB)

Phan, The-Long; Ho, T.A. [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Thang, P.D. [Faculty of Engineering Physics and Nanotechnology, VNU-University of Engineering and Technology, Xuan Thuy, Cau Giay, Hanoi (Viet Nam); Tran, Q.T. [Center for Science and Technology Communication, Ministry of Science and Technology, 113 Tran Duy Hung, Hanoi (Viet Nam); Thanh, T.D.; Phuc, N.X. [Institute of Materials Science, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi (Viet Nam); Phan, M.H. [Department of Physics, University of South Florida, Tampa, FL 33620 (United States); Huy, B.T. [Department of Chemistry, Changwon National University, Changwon 641-773 (Korea, Republic of); Yu, S.C., E-mail: scyu@chungbuk.ac.kr [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of)

2014-12-05

Highlights: • Tricritical point in Y-doped Nd{sub 0.7}Sr{sub 0.3}MnO{sub 3} manganites. • A large magnetic-entropy change. • Magnetic inhomogeneity and phase separation. - Abstract: We have determined the values of critical exponents of two polycrystalline samples (Nd{sub 1−x}Y{sub x}){sub 0.7}Sr{sub 0.3}MnO{sub 3} (x = 0 and 0.07) from the magnetization data versus temperature and magnetic field, M(H, T), to learn about their magnetic and magnetocaloric (MC) properties. The results reveal the samples exhibiting the crossover of first-order and second-order phase transitions, where the exponent values β = 0.271 and γ = 0.922 for x = 0, and β = 0.234–0.236 and γ = 1.044–1.063 for x = 0.07 determined by using modified Arrott plots and static-scaling hypothesis are close to those expected for the tricritical mean-field theory (β = 0.25 and γ = 1.0). Particularly, the T{sub C} of x = 0 and 0.07 can be any value in the temperature ranges of 240–255 K and 170–278 K, respectively, depending on the magnitude of applied magnetic field and determination techniques. Around the T{sub C}, studying the MC effect of the samples has revealed a large magnetic-entropy change (ΔS{sub m}) up to ∼8 J/kg K for the applied field interval ΔH = 50 kOe, corresponding to refrigerant capacity values of 200–245 J/kg. These phenomena are related to the crossover nature and the persisting of FM/anti-FM interactions even above the T{sub C}, as further confirmed by electron-spin-resonance data, Curie–Weiss law-based analyses, and an exponential parameter characteristic of magnetic order n = dLn|ΔS{sub m}|/dLnH.

Observation of the strain-driven charge-ordered state in La sub 0 sub . sub 7 sub C a sub 0 sub . sub 3 MnO sub 3 sub - sub d elta thin film with oxygen deficiency

CERN Document Server

Prokhorov, V G; Kaminsky, G G; Svetchnikov, V L; Zandbergen, H W; Lee, Y P; Park, J S; Kim, K W

2003-01-01

The magnetic and transport properties of La sub 0 sub . sub 7 Ca sub 0 sub . sub 3 MnO sub 3 sub - sub d elta films with an oxygen deficiency (delta approx 0.1) and a La sub 0 sub . sub 9 Ca sub 0 sub . sub 1 MnO sub 3 film with the stoichiometric oxygen content are investigated in a wide temperature range. It is shown that the charge-ordered insulating (COI) state is observed for a La sub 0 sub . sub 7 Ca sub 0 sub . sub 3 MnO sub 2 sub . sub 9 film with thickness d <= 30 nm, which manifests mainly a cubic crystal structure with an anomalously small lattice parameter for this composition. An increase in the film thickness (d approx 60 nm) leads to a structural transition from the lattice-strained cubic to the relaxed rhombohedral phase, is accompanied by a shift of the Curie point (T sub C) to lower temperature and a frustration of the COI state. The magnetic and transport properties of the La sub 0 sub . sub 7 Ca sub 0 sub . sub 3 MnO sub 2 sub . sub 9 film with d approx 60 nm are similar to those exhibi...

Electronic transport in the heavy fermion superconductors UPd{sub 2}Al{sub 3} and UNi{sub 2}Al{sub 3}. Thin film studies

Energy Technology Data Exchange (ETDEWEB)

Foerster, Michael

2008-07-01

This work addresses the electronical properties of the superconductors UPd{sub 2}Al{sub 3} and UNi{sub 2}Al{sub 3} on the basis of thin film experiments. Epitaxial thin film samples of UPd{sub 2}Al{sub 3} and UNi{sub 2}Al{sub 3} were prepared using UHV Molecular Beam Epitaxy (MBE). For UPd{sub 2}Al{sub 3}, the change of the growth direction from the intrinsic (001) to epitaxial (100) was predicted and sucessfully demonstrated using LaAlO3 substrates cut in (110) direction. With optimized deposition process parameters for UPd{sub 2}Al{sub 3} (100) on LaAlO{sub 3}(110) superconducting samples with critical temperatures up to T{sub c}=1.75 K were obtained. UPd{sub 2}Al{sub 3}-AlO{sub x}-Ag mesa junctions with superconducting base electrode were prepared and shown to be in the tunneling regime. However, no signatures of a superconducting density of states were observed in the tunneling spectra. The resistive superconducting transition was probed for a possible dependence on the current direction. In contrast to UNi{sub 2}Al{sub 3}, the existence of such feature was excluded in UPd{sub 2}Al{sub 3}(100) thin films. The second focus of this work is the dependence of the resistive transition in UNi{sub 2}Al{sub 3}(100) thin films on the current direction. The experimental fact that the resistive transition occurs at slightly higher temperatures for I parallel a than for I parallel c can be explained within a model of two weakly coupled superconducting bands. Evidence is presented for the key assumption of the two-band model, namely that transport in and out of the ab-plane is generated on different, weakly coupled parts of the Fermi surface. Main indications are the angle dependence of the superconducting transition and the dependence of the upper critical field B{sub c{sub 2}} on current and field orientation. Additionally, several possible alternative explanations for the directional splitting of the transition are excluded in this work. An origin due to scattering on

A vibrating membrane bioreactor operated at supra- and sub-critical flux: Influence of extracellular polymeric substances from yeast cells

DEFF Research Database (Denmark)

Beier, Søren Prip; Jonsson, Gunnar Eigil

2007-01-01

A vibrating membrane bioreactor, in which the fouling problems are reduced by vibrating a hollow fiber membrane module, has been tested in constant flux microfiltration above (supra-critical) and below (sub-critical) an experimentally determined critical flux. Suspensions of bakers yeast cells were...... chosen as filtration medium (dry weight 4 g/l). The influence of extracellular polymeric substances (EPS) from the yeast cells is evaluated by UV absorbance measurements of the bulk supernatant during filtration. The critical flux seems to be an interval or a relative value rather than an absolute value....... Filtration just below the critical flux (sub-critical) seems to be a good compromise between acceptable flux level and acceptable increase of fouling resistance and trans-membrane pressure (TMP) in a given time period. EPS from the yeast cells causes the membrane module to foul and part of the fouling...

Consistent Set of Experiments from ICSBEP Handbook for Evaluation of Criticality Calculation Prediction of Apparatus of External Fuel Cycle with Different Fuel

Energy Technology Data Exchange (ETDEWEB)

Golovko, Yury E. [FSUE ' SSC RF-IPPE' , 249033, Bondarenko Square 1, Obninsk (Russian Federation)

2008-07-01

Experiments with plutonium, low enriched uranium and uranium-233 from the ICSBEP1 Handbook are being considered in this paper. Among these experiments it was selected only those, which seem to be the most relevant to the evaluation of uncertainty of critical mass of mixtures of plutonium or low enriched uranium or uranium-233 with light water. All selected experiments were examined and covariance matrices of criticality uncertainties were developed along with some uncertainties were revised. Statistical analysis of these experiments was performed and some contradictions were discovered and eliminated. Evaluation of accuracy of prediction of criticality calculations was performed using the internally consistent set of experiments with plutonium, low enriched uranium and uranium-233 remained after the statistical analyses. The application objects for the evaluation of calculational prediction of criticality were water-reflected spherical systems of homogeneous aqueous mixtures of plutonium or low enriched uranium or uranium-233 of different concentrations which are simplified models of apparatus of external fuel cycle. It is shows that the procedure allows to considerably reduce uncertainty in k{sub eff} caused by the uncertainties in neutron cross-sections. Also it is shows that the results are practically independent of initial covariance matrices of nuclear data uncertainties. (authors)

Development and assessment of a sub-channel code applicable for trans-critical transient of SCWR

International Nuclear Information System (INIS)

Liu, X.J.; Yang, T.; Cheng, X.

2013-01-01

Highlights: • A new sub-channel code COBRA-SC for SCWR is developed. • Pseudo two-phase method is employed to realize trans-critical transient calculation. • Good suitability of COBRA-SC is demonstrated by preliminary assessment. • The calculation results of COBRA-SC agree well with ATHLET code. -- Abstract: In the last few years, extensive R and D activities have been launched covering various aspects of supercritical water-cooled reactor (SCWR), especially the thermal-hydraulic analysis. Sub-channel code plays an indispensable role to predict the detail thermal-hydraulic behavior of the SCWR fuel assembly. This paper develops a new version of sub-channel code COBRA-SC based on the previous COBRA-IV code. The supercritical water property and heat transfer/pressure drop correlations under supercritical pressure are implemented to this code. Moreover, in order to simulate the trans-critical transient (the pressure undergo a decrease from the supercritical pressure to the subcritical pressure), pseudo two-phase method is employed in COBRA-SC code. This work is completed by introduction of a virtual two-phase region near the pseudo-critical line. A smooth transition of void fraction can be realized. In addition, several heat transfer correlations right underneath the critical point are introduced into this code to capture the heat transfer behavior during the trans-critical transient. Some experimental data from simple geometry, e.g. the single tube, small rod bundle, is used to validate and evaluate this new developed COBRA-SC code. The predicted results show a good agreement with the experimental data, demonstrating good feasibility of this code for SCWR condition. A code to code comparison between COBRA-SC and ATHLET for a blowdown transient of a small fuel assembly is also presented and discussed in this paper

Heavy water critical experiments on plutonium lattice

International Nuclear Information System (INIS)

Miyawaki, Yoshio; Shiba, Kiminori

1975-06-01

This report is the summary of physics study on plutonium lattice made in Heavy Water Critical Experiment Section of PNC. By using Deuterium Critical Assembly, physics study on plutonium lattice has been carried out since 1972. Experiments on following items were performed in a core having 22.5 cm square lattice pitch. (1) Material buckling (2) Lattice parameters (3) Local power distribution factor (4) Gross flux distribution in two region core (5) Control rod worth. Experimental results were compared with theoretical ones calculated by METHUSELAH II code. It is concluded from this study that calculation by METHUSELAH II code has acceptable accuracy in the prediction on plutonium lattice. (author)

Discrete Event Modeling and Simulation-Driven Engineering for the ATLAS Data Acquisition Network

CERN Document Server

Bonaventura, Matias Alejandro; The ATLAS collaboration; Castro, Rodrigo Daniel

2016-01-01

We present an iterative and incremental development methodology for simulation models in network engineering projects. Driven by the DEVS (Discrete Event Systems Specification) formal framework for modeling and simulation we assist network design, test, analysis and optimization processes. A practical application of the methodology is presented for a case study in the ATLAS particle physics detector, the largest scientific experiment built by man where scientists around the globe search for answers about the origins of the universe. The ATLAS data network convey real-time information produced by physics detectors as beams of particles collide. The produced sub-atomic evidences must be filtered and recorded for further offline scrutiny. Due to the criticality of the transported data, networks and applications undergo careful engineering processes with stringent quality of service requirements. A tight project schedule imposes time pressure on design decisions, while rapid technology evolution widens the palett...

Comparison study of hybrid VS critical systems in point kinetics

International Nuclear Information System (INIS)

Ritter, G.; Tommasi, J.; Slessarev, L.; Salvatores, M.; Mouney, H.; Vergnes, J.

1999-01-01

An essential motivation for hybrid systems is a potentially high level of intrinsic safety against reactivity accidents. In this respect, it is necessary to assess the behaviour of an Accelerator Driven System during a TOP, LOF or TOC accident. A comparison between a critical and sub-critical reactor shows a larger sensitivity for the critical system. The ADS has an unquestionable advantage in case of TOP but a less favourable behaviour as for LOFWS type of accidents. However in the ADS cases, the beam could be easily shut off during the transient. Therefore, a part of the R and D effort should be focused on the monitoring and control of power. (author)

Fluctuation dynamics near the quantum critical point in the S=1/2 Ising chain CoNb{sub 2}O{sub 6}

Energy Technology Data Exchange (ETDEWEB)

Harms, Steffen; Engelmayer, Johannes; Lorenz, Thomas; Hemberger, Joachim [II. Physikalisches Institut, Koeln Univ. (Germany)

2016-07-01

CoNb{sub 2}O{sub 6} is a model system for quantum phase transitions in magnetic field. Its structure consists of layers of CoO{sub 6} octahedrons separated by non-magnetic NbO{sub 6} layers. The edge-sharing oxygen octahedrons link the Co{sup 2+} spins via Co-O-Co superexchange and form 1D ferromagnetic zigzag chains along the orthorhombic c axis. Crystal field effects lead to an easy-axis anisotropy of the Co{sup 2+} moments in the ac plane and to an effective spin-1/2 chain system. The 1D spin system can be described by the Ising model. At T=0 K a transverse magnetic field can induce a quantum phase transition from a long range ferromagnetic state into a quantum paramagnetic state. Employing measurements of the complex AC-susceptibility in the frequency range 10 MHz < ν < 5 GHz for temperatures down to 50 mK we investigate the slowing down of the magnetic fluctuation dynamics in the vicinity of the critical field at μ{sub 0}H=5.25 T.

Information theory explanation of the fluctuation theorem, maximum entropy production and self-organized criticality in non-equilibrium stationary states

CERN Document Server

Dewar, R

2003-01-01

Jaynes' information theory formalism of statistical mechanics is applied to the stationary states of open, non-equilibrium systems. First, it is shown that the probability distribution p subGAMMA of the underlying microscopic phase space trajectories GAMMA over a time interval of length tau satisfies p subGAMMA propor to exp(tau sigma subGAMMA/2k sub B) where sigma subGAMMA is the time-averaged rate of entropy production of GAMMA. Three consequences of this result are then derived: (1) the fluctuation theorem, which describes the exponentially declining probability of deviations from the second law of thermodynamics as tau -> infinity; (2) the selection principle of maximum entropy production for non-equilibrium stationary states, empirical support for which has been found in studies of phenomena as diverse as the Earth's climate and crystal growth morphology; and (3) the emergence of self-organized criticality for flux-driven systems in the slowly-driven limit. The explanation of these results on general inf...

Experiments on vibration-driven stick-slip locomotion: A sliding bifurcation perspective

Science.gov (United States)

Du, Zhouwei; Fang, Hongbin; Zhan, Xiong; Xu, Jian

2018-05-01

Dry friction appears at the contact interface between two surfaces and is the source of stick-slip vibrations. Instead of being a negative factor, dry friction is essential for vibration-driven locomotion system to take effect. However, the dry-friction-induced stick-slip locomotion has not been fully understood in previous research, especially in terms of experiments. In this paper, we experimentally study the stick-slip dynamics of a vibration-driven locomotion system from a sliding bifurcation perspective. To this end, we first design and build a vibration-driven locomotion prototype based on an internal piezoelectric cantilever. By utilizing the mechanical resonance, the small piezoelectric deformation is significantly amplified to drive the prototype to achieve effective locomotion. Through identifying the stick-slip characteristics in velocity histories, we could categorize the system's locomotion into four types and obtain a stick-slip categorization diagram. In each zone of the diagram the locomotion exhibits qualitatively different stick-slip dynamics. Such categorization diagram is actually a sliding bifurcation diagram; crossing from one stick-slip zone to another corresponds to the triggering of a sliding bifurcation. In addition, a simplified single degree-of-freedom model is established, with the rationality of simplification been explained theoretically and numerically. Based on the equivalent model, a numerical stick-slip categorization is also obtained, which shows good agreement with the experiments both qualitatively and quantitatively. To the best of our knowledge, this is the first work that experimentally generates a sliding bifurcation diagram. The obtained stick-slip categorizations deepen our understanding of stick-slip dynamics in vibration-driven systems and could serve as a base for system design and optimization.

Experiences of leadership in health care in sub-Saharan Africa.

Science.gov (United States)

Curry, Leslie; Taylor, Lauren; Chen, Peggy Guey-Chi; Bradley, Elizabeth

2012-09-13

Leadership is widely regarded as central to effective health-care systems, and resources are increasingly devoted to the cultivation of strong health-care leadership. Nevertheless, the literature regarding leadership capacity building has been developed primarily in the context of high-income settings. Less research has been done on leadership in low-income settings, including sub-Saharan Africa, particularly in health care, with attention to historical, political and sociocultural context. We sought to characterize the experiences of individuals in key health-care leadership roles in sub-Saharan Africa. We conducted a qualitative study using in-person interviews with individuals (n = 17) in health-care leadership roles in four countries in sub-Saharan Africa: the Federal Democratic Republic of Ethiopia, the Republic of Ghana, the Republic of Liberia and the Republic of Rwanda. Individuals were identified by their country's minister of health as key leaders in the health sector and were nominated to serve as delegates to a global health leadership conference in June 2010, at Yale University in the United States. Interviews were audio recorded and professionally transcribed. Data analysis was performed by a five-person multidisciplinary team using the constant comparative method, facilitated by ATLAS.ti 5.0 software. Five key themes emerged as important to participants in their leadership roles: having an aspirational, value-based vision for improving the future health of the country, being self-aware and having the ability to identify and use complementary skills of others, tending to relationships, using data in decision making, and sustaining a commitment to learning. Current models of leadership capacity building address the need for core technical and management competencies. While these competencies are important, skills relevant to managing relationships are also critical in the sub-Saharan African context. Developing such skills may require more time and

Ability to burn plutonium and minor actinides. Interest of accelerator driven system compared to critical reactor

International Nuclear Information System (INIS)

Vergnes, J.; Mouney, H.

1998-01-01

In the frame of the French Act of December 1991, EDF is presently assessing the interest of Acceleration Driven System (ADS) for the Transmutation of the Plutonium and Minor Actinides (MA) produced by its park of nuclear reactors. The studies presented here assess the efficiency of ADS and critical reactors to incinerate Pu and MA (Minor Actinides) and the potential interest of ADS for that purpose. (author)

Synthesis, surface and optical properties of Ag{sub 2}CaV{sub 4}O{sub 12} nanoparticles for dye removal under visible irradiation

Energy Technology Data Exchange (ETDEWEB)

Lu, Yuting [State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123 (China); Wan, Yingpeng [Department of Physics and Interdisciplinary Program of Biomedical, Mechanical & Electrical Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of); Bi, Shala; Weng, Honggen [State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123 (China); Huang, Yanlin, E-mail: huang@suda.edu.cn [State and Local Joint Engineering Laboratory for Novel Functional Polymeric Materials, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123 (China); Qin, Lin [Department of Physics and Interdisciplinary Program of Biomedical, Mechanical & Electrical Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of); Seo, Hyo Jin, E-mail: hjseo@pknu.ac.kr [Department of Physics and Interdisciplinary Program of Biomedical, Mechanical & Electrical Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of)

2016-09-01

Ag-containing compounds are regarded as potential candidates for the efficient photocatalyst driven by visible-light. In this work, nano-sized Ag{sub 2}CaV{sub 4}O{sub 12} was prepared via a modified Pechini synthesis. The detailed structural refinement of X-ray diffraction (XRD) pattern indicates that the Ag{sub 2}CaV{sub 4}O{sub 12} crystallizes in tetragonal system with the space group of P4/nbm (125), Z = 2. The surface property of this vanadate was measured by the scanning electron microscope (SEM), energy dispersive spectra (EDS), transmission electron microscopy (TEM), and nitrogen adsorption-desorption isotherm. The sample has an efficient optical absorption in the wavelength from UV to visible region characterized by its narrow band-gap energy of 2.231 eV with an indirect allowed property. The valence band maximum is composed of multiple states of Ag-d and O-p resulting in a narrow band. The excellent photocatalytic activity of Ag{sub 2}CaV{sub 4}O{sub 12} nanoparticles was tested by the photodegradation of rhodamine B (RhB), methylene blue (MB) and phenol solutions excited by visible-light. The photocatalytic mechanism was suggested according to experimental results and the band energy positions. - Highlights: • A new visible-light-driven photocatalyst of Ag{sub 2}CaV{sub 4}O{sub 12} was developed. • It has a narrow band gap of 2.231 eV with an indirect allowed characteristic. • Ag{sub 2}CaV{sub 4}O{sub 12} shows high activity in the MB degradation under visible light. • The photocatalytic ability is mainly driven by the ·OH radicals.

Contributions to the qualification of the ''CRISTAL'' criticality calculi scheme: interpretation of critical experiments. Elaboration of a characterization system of neutronic configurations; Contributions a la qualification du schema de calcul de criticite ''cristal'': interpretation d'experiences critiques. Elaboration d'un systeme de caracterisation des configurations neutroniques

Energy Technology Data Exchange (ETDEWEB)

Gagnier, E

1999-06-01

This thesis work is about the validation of the new criticality-safety package CRISTAL and contributes to the modernization and the improvement of the computational tools. The first part presents neutronic elements, the objectives of safety criticality studies and the package CRISTAL. Then, the validation work concerned two series of experiments involving uranyl solutions (UO{sub 2}F{sub 2}) and UO{sub 2} powders. For these experiments, the differences between the computation results and the experimental results were analysed. It was highlighted interesting physical phenomena such of the compensations of errors between the approximate representation by the 99 energy group structure on the first resonance of oxygen and the anisotropy of the diffusion simulation as well as the influence of uranium 234 in high enriched solutions in uranium 235. Once the work of the experimental qualification carried out, raises the question of the use the base of qualification and the ''calculation-experiment'' variations which are referred to it. It is often difficult to establish the link between the ''studied configuration'' and the experiments of the base of qualification. The presented characterisation system proposes to answer in a way automatic and quantified this difficulty: - in bringing an answer on the package qualification for the studied configuration, - in giving an estimate of the package bias. To answer these points, it was defined a set of 35 characteristic neutronic parameters representing the behaviour of the medium. To process the information brought by these parameters and to use it to answer the objectives of the system, we called upon statistical methods (Principal Components Analysis and Sliced Inverse Regression). The results obtained in the feasibility studies showed the relevance of these methods for the considered objectives. (author)

Improved solar-driven photocatalytic performance of Ag{sub 2}CO{sub 3}/(BiO){sub 2}CO{sub 3} prepared in-situ

Energy Technology Data Exchange (ETDEWEB)

Zhong, Junbo, E-mail: junbozhong@163.com [Key Laboratory of Green Catalysis of Higher Education Institutes of Sichuan, College of Chemistry and Pharmaceutical Engineering, Sichuan University of Science and Engineering, Zigong 643000 (China); Li, Jianzhang, E-mail: lschmanuscript@163.com [Key Laboratory of Green Catalysis of Higher Education Institutes of Sichuan, College of Chemistry and Pharmaceutical Engineering, Sichuan University of Science and Engineering, Zigong 643000 (China); Huang, Shengtian; Cheng, Chaozhu; Yuan, Wei [Key Laboratory of Green Catalysis of Higher Education Institutes of Sichuan, College of Chemistry and Pharmaceutical Engineering, Sichuan University of Science and Engineering, Zigong 643000 (China); Li, Minjiao [Key Laboratory of Green Catalysis of Higher Education Institutes of Sichuan, College of Chemistry and Pharmaceutical Engineering, Sichuan University of Science and Engineering, Zigong 643000 (China); Sichuan Provincial Academician (Expert) Workstation, Sichuan University of Science and Engineering, Zigong 643000 (China); Ding, Jie [Key Laboratory of Green Catalysis of Higher Education Institutes of Sichuan, College of Chemistry and Pharmaceutical Engineering, Sichuan University of Science and Engineering, Zigong 643000 (China)

2016-05-15

Highlights: • Ag{sub 2}CO{sub 3}/(BiO){sub 2}CO{sub 3} photocatalysts were prepared in-situ. • The photo-induced charge separation rate has been greatly increased. • The photocatalytic activity has been greatly promoted. - Abstract: Ag{sub 2}CO{sub 3}/(BiO){sub 2}CO{sub 3} composites have been fabricated in-situ via a facile parallel flaw co-precipitation method. The specific surface area, structure, morphology, and the separation rate of photo-induced charge pairs of the photocatalysts were characterized by Brunauer–Emmett–Teller (BET) method, X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy(DRS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and surface photovoltage (SPV) spectroscopy, respectively. XRD patterns and DRS demonstrated that Ag{sub 2}CO{sub 3} has no effect on the crystal phase and bandgap of (BiO){sub 2}CO{sub 3}. The existence of Ag{sub 2}CO{sub 3} in the composites enhances the separation rate of photo-induced charge pairs of the photocatalysts. The photocatalytic performance of Ag{sub 2}CO{sub 3}/(BiO){sub 2}CO{sub 3} was evaluated by the decolorization of methyl orange (MO) aqueous solution under simulated solar irradiation. It was found that the simulated solar-induced photocatalytic activity of Ag{sub 2}CO{sub 3}/(BiO){sub 2}CO{sub 3} copmposites was significantly improved, which was mainly attributed to the enhanced surface area and the separation rate of photo-induced charge pairs.

Critical Experiments With Aqueous Solutions of 233UO2(NO3)2

International Nuclear Information System (INIS)

Thomas, J.T.

2001-01-01

This report provides the critical experimenter's interpretations and descriptions of informal critical experiment logbook notes and associated information (e.g., experimental equipment designs/sketches, chemical and isotopic analyses, etc.) for the purpose of formally documenting the results of critical experiments performed in the late 1960s at the Oak Ridge Critical Experiments Facility. The experiments were conducted with aqueous solutions of 97.6 wt % 233 U uranyl nitrate having uranium densities varying between about 346 g U/l and 45 g U/l. Criticality was achieved with single simple units (e.g., cylinders and spheres) and with spaced subcritical simple cylindrical units arranged in unreflected, water-reflected, and polyethylene reflected critical arrays

Pathways and pipelines: Self-reported critical experiences for expert and novice geologists

Science.gov (United States)

LaDue, N.; Pacheco, H. A.

2011-12-01

The recruitment and retention of geology students has received attention due to pressure from industry to replenish an aging workforce nearing retirement (Gonzales and Keane, 2010). Thorough, qualitative studies have been conducted using critical incident methodology to understand what experiences cause various groups of people to choose careers in the geosciences or geoscience degree programs (Levine et al., 2007; Houlton, 2010). This study both builds upon earlier studies and provides new insights about capacity building in the geosciences. Individuals who have been successfully pipelined into the geosciences ranging from upper-level undergraduates to decades-long professionals, were selected for an expert-novice study about field mapping. All of the 38 participants have field-mapping experience and were selected to achieve a balance of age, gender and experience in the sample and secondarily based on geographic diversity. Participants were asked how they became interested in geology as the last question of an interview about the other tasks during the study. Participants were surficially probed, in contrast to in-depth interviews conducted using critical incident methods. Remarkably, though the interview question was unstructured and open ended, the three persistent themes that emerged are consistent with previous studies of women geologists (Holmes and O'Connell, 2003), under-represented minorities (Levine et al., 2007), and undergraduate geoscience majors (Houlton, 2010): Role or influence of academic experience, influence of and/or connections with people and connections with Earth. Additionally, individual participant comments are well aligned the proposed framework by Kraft et al. (2011) for engaging geoscience students through the affective domain. We suggest that future studies should examine whether these findings are consistent across geologists from sub-domains that are less field-based and involve primarily modeling, or other computer- and lab

Critical velocities in He II for independently varied superfluid and normal fluid velocities

International Nuclear Information System (INIS)

Baehr, M.L.

1984-01-01

Experiments were performed to measure the critical velocity in pure superflow and compare to the theoretical prediction; to measure the first critical velocity for independently varied superfluid and normal fluid velocities; and to investigate the propagation of the second critical velocity from the thermal counterflow line through the V/sub n/,-V/sub s/ quadrant. The experimental apparatus employed a thermal counterflow heater to adjust the normal fluid velocity, a fountain pump to vary the superfluid velocity, and a level sensing capacitor to measure the superfluid velocity. The results of the pure superfluid critical velocity measurements indicate that this velocity is temperature independent contrary to Schwarz's theory. It was found that the first critical velocity for independently varied V/sub n/ and V/sub s/ could be described by a linear function of V/sub n/ and was otherwise temperature independent. It was found that the second critical velocity could only be distinguished near the thermal counterflow line

Urenco`s experience of UF{sub 6} handling

Energy Technology Data Exchange (ETDEWEB)

Saelmans, F. [Urenco Almelo (Netherlands); Scane, C. [Urenco Capenhurst (United Kingdom); Christofzik, J. [Urenco Gronau (Germany)

1991-12-31

Urenco operates enrichment plants at three sites, Almelo (Netherlands), Capenhurst (United Kingdom) and Gronau (Germany). Current installed separative work capacity is 2,500 tSWpa. Since 1971, when the first pilot plants were built, enrichment production has totalled 18,000 tSW. During this last 20 years over 3,500 48 containers of UF{sub 6} have been fed to the plants, over 3,700 30 containers have been filled with product and delivered successfully to Urenco`s customers worldwide and over 3,000 48 containers of depleted tails have been filled and have either been returned to customers or retained for long term storage on site. The paper gives a brief outline of Urenco`s experience in handling UF{sub 6}: the equipment and methods used in receiving, feeding, filling, blending, liquid sampling, storing, moving on site and despatching of UF{sub 6} containers. Some of the difficulties experienced with UF{sub 6} containers are appended.

Second order magnetic phase transition and scaling analysis in iron doped manganite La{sub 0.7}Ca{sub 0.3}Mn{sub 1−x}Fe{sub x}O{sub 3} compounds

Energy Technology Data Exchange (ETDEWEB)

Ginting, Dianta [Department of Applied Physics and Institute of Natural Sciences, Kyung Hee University, Yong-in 446-701 (Korea, Republic of); Nanto, Dwi [Physics Education, Syarif Hidayatullah State Islamic University, Jakarta 15412 (Indonesia); Denny, Yus Rama [Department of Electrical Engineering, University of Sultan Ageng Tirtayasa, Banten 42435 (Indonesia); Tarigan, Kontan [Department of Mechanical Engineering, Mercu Buana University, Jakarta-Barat, Jakarta 11650 (Indonesia); Hadi, Syamsul [Department of Mechanical Engineering, State Polytechnic of Malang, East Java 65100 (Indonesia); Ihsan, Mohammad [PSTBM-BATAN, Kawasan Puspiptek Serpong, Tangerang Selatan, Banten 15314 (Indonesia); Institute of Electronic Materials, University of Wollongong, Wollongong NSW 2522 (Australia); Rhyee, Jong-Soo, E-mail: jsrhyee@khu.ac.kr [Department of Applied Physics and Institute of Natural Sciences, Kyung Hee University, Yong-in 446-701 (Korea, Republic of)

2015-12-01

We investigated magnetic properties of La{sub 0.7}Ca{sub 0.3}Mn{sub 1−x}Fe{sub x}O{sub 3} (x=0.09 and 0.11) compounds in terms of isothermal magnetization analysis and scaling behavior with various critical exponents. From the Landau theory of magnetic phase transition, we found that the paramagnetic to ferromagnetic phase transition in La{sub 0.7}Ca{sub 0.3}Mn{sub 1−x}Fe{sub x}O{sub 3} (x=0.09 and 0.11) compounds is the type of second order magnetic transition (SOMT), which contrary to the first order magnetic transition (FOMT) for low Fe-doped compounds (x<0.09) in previous reports. When we investigate the critical behavior of the compounds near T=T{sub c} by the modified Arrott plot, Kouvel–Fisher plots, and critical isothermal analysis, the estimated critical exponents β, γ, and δ are in between the theoretically predicted values for three-dimensional Heisenberg and mean-field interaction models. It is noteworthy that the scaling relations are obeyed in terms of renormalization magnetization m=ε{sup −β}M(H,ε) and renormalized field h=|ε|{sup β+γ}H. Temperature-dependent effective exponents β{sub eff} and γ{sub eff} correspond to the ones of disordered ferromagnets. It is shown that the magnetic state of the compounds is not fully described by the conventional localized-spin interaction model because the ferromagnetic interaction has itinerant character by increasing Fe-doping concentration. - Highlights: • The ferromagnetic phase transition is of second order in La{sub 0.7}Ca{sub 0.3}Mn{sub 1−x}Fe{sub x}O{sub 3}. • The critical exponents are in between the 3D Heisenberg and mean-field models. • The ferromagnetic interaction becomes more itinerant by Fe-doping.

KUCA critical experiments using MEU fuel (II)

Energy Technology Data Exchange (ETDEWEB)

Kanda, Keiji; Hayashi, Masatoshi; Shiroya, Seiji; Kobayashi, Keiji; Fukui, Hiroshi; Mishima, Kaichiro; Shibata, Toshikazu [Research Reactor Institute, Kyoto University, Kumatori-cho, Sennan-gun, Osaka (Japan)

1983-09-01

Due to mutual concerns in the USA and Japan about the proliferation potential of highly-enriched uranium (HEU), a joint study program I was initiated between Argonne National Laboratory (ANL and Kyoto University Research Reactor Institute (KURRI) in 1978. In accordance with the reduced enrichment for research and test reactor (RERTR) program, the alternatives were studied for reducing the enrichment of the fuel to be used in the Kyoto University High Flux Reactor (KUHFR). The KUHFR has a distinct feature in its core configuration it is a coupled-core. Each annular shaped core is light-water-moderated and placed within a heavy water reflector with a certain distance between them. The phase A reports of the joint ANL-KURRI program independently prepared by two laboratories in February 1979, 3,4 concluded that the use of medium-enrichment uranium (MEU, 45%) in the KUHFR is feasible, pending results of the critical experiments in the Kyoto University Critical Assembly (KUCA) 5 and of the burnup test in the Oak Ridge Research Reactor 6 (ORR). An application of safety review (Reactor Installation License) for MEU fuel to be used in the KUCA was submitted to the Japanese Government in March 1980, and a license was issued in August 1980. Subsequently, the application for 'Authorization before Construction' was submitted and was authorized in September 1980. Fabrication of MEU fuel-elements for the KUCA experiments by CERCA in France was started in September 1980, and was completed in March 1981. The critical experiments in the KUCA with MEU fuel were started on a single-core in May 1981 as a first step. The first critical state of the core using MEU fuel was achieved at 312 p.m. in May 12, 1981. After that, the reactivity effects of the outer side-plates containing boron burnable poison were measured. At Munich Meeting in Sept., 1981, we presented a paper on critical mass and reactivity of burnable poison in the MEU core. Since then we carried out the following experiments

KUCA critical experiments using MEU fuel (II)

International Nuclear Information System (INIS)

Kanda, Keiji; Hayashi, Masatoshi; Shiroya, Seiji; Kobayashi, Keiji; Fukui, Hiroshi; Mishima, Kaichiro; Shibata, Toshikazu

1983-01-01

Due to mutual concerns in the USA and Japan about the proliferation potential of highly-enriched uranium (HEU), a joint study program I was initiated between Argonne National Laboratory (ANL and Kyoto University Research Reactor Institute (KURRI) in 1978. In accordance with the reduced enrichment for research and test reactor (RERTR) program, the alternatives were studied for reducing the enrichment of the fuel to be used in the Kyoto University High Flux Reactor (KUHFR). The KUHFR has a distinct feature in its core configuration it is a coupled-core. Each annular shaped core is light-water-moderated and placed within a heavy water reflector with a certain distance between them. The phase A reports of the joint ANL-KURRI program independently prepared by two laboratories in February 1979, 3,4 concluded that the use of medium-enrichment uranium (MEU, 45%) in the KUHFR is feasible, pending results of the critical experiments in the Kyoto University Critical Assembly (KUCA) 5 and of the burnup test in the Oak Ridge Research Reactor 6 (ORR). An application of safety review (Reactor Installation License) for MEU fuel to be used in the KUCA was submitted to the Japanese Government in March 1980, and a license was issued in August 1980. Subsequently, the application for 'Authorization before Construction' was submitted and was authorized in September 1980. Fabrication of MEU fuel-elements for the KUCA experiments by CERCA in France was started in September 1980, and was completed in March 1981. The critical experiments in the KUCA with MEU fuel were started on a single-core in May 1981 as a first step. The first critical state of the core using MEU fuel was achieved at 312 p.m. in May 12, 1981. After that, the reactivity effects of the outer side-plates containing boron burnable poison were measured. At Munich Meeting in Sept., 1981, we presented a paper on critical mass and reactivity of burnable poison in the MEU core. Since then we carried out the following experiments

Fabrication of heterostructured Bi{sub 2}O{sub 2}CO{sub 3}/Bi{sub 2}O{sub 4} photocatalyst and efficient photodegradation of organic contaminants under visible-light

Energy Technology Data Exchange (ETDEWEB)

Sun, Meng; Li, Shuangli; Yan, Tao; Ji, Pengge; Zhao, Xia; Yuan, Kun; Wei, Dong [School of Resources and Environment, University of Jinan, Jinan 250022 (China); Du, Bin, E-mail: dubin61@gmail.com [School of Resources and Environment, University of Jinan, Jinan 250022 (China); Key Laboratory of Chemical Sensing & Analysis in Universities of Shandong, School of Chemistry and Chemical Engineering, University of Jinan, Jinan 250022 (China)

2017-07-05

Highlights: • The product shows efficient activity in photodegradation of RhB, BPA, and phenol. • The BBOC-10 heterojunction exhibits the best activity under visible light. • Suppressed recombination of photo-generated carriers lead to the activity enhancement. - Abstract: Heterostructured Bi{sub 2}O{sub 2}CO{sub 3}/Bi{sub 2}O{sub 4} photocatalysts were fabricated by a facile one-pot hydrothermal method, in which melem served as the sacrificial reagent to supply carbonate anions. The as-synthesized Bi{sub 2}O{sub 2}CO{sub 3}/Bi{sub 2}O{sub 4} heterojunction catalysts were characterized by X-ray diffraction, UV–vis diffuse reflectance spectra, X-ray photoelectron spectroscopy, scanning electron microscope, and transmission electron microscope. The XRD patterns of Bi{sub 2}O{sub 2}CO{sub 3}/Bi{sub 2}O{sub 4} catalysts showed the distinctive peaks of Bi{sub 2}O{sub 2}CO{sub 3} and Bi{sub 2}O{sub 4}. The SEM and TEM results showed that the pure Bi{sub 2}O{sub 2}CO{sub 3} possessed large plate morphology, while Bi{sub 2}O{sub 4} were composed of various nanorods and particles. As for Bi{sub 2}O{sub 2}CO{sub 3}/Bi{sub 2}O{sub 4} heterojunction, it was obviously observed that Bi{sub 2}O{sub 4} nanorods and particles were grown on the surfaces of Bi{sub 2}O{sub 2}CO{sub 3} plates. The visible light driven photocatalytic activity of Bi{sub 2}O{sub 2}CO{sub 3}/Bi{sub 2}O{sub 4} heterojunction photocatalyst was evaluated by decomposing dyes, phenol, and bisphenol A in water. Compared with Bi{sub 2}O{sub 2}CO{sub 3} and Bi{sub 2}O{sub 4}, the Bi{sub 2}O{sub 2}CO{sub 3}/Bi{sub 2}O{sub 4} photocatalysts have exhibited remarkable enhanced activity under visible light. The excellent activity can be mainly attributed to the enhanced separation efficiency of photo-generated carriers. Controlled experiments using different radical scavengers proved that ·O{sub 2}{sup −} and h{sup +} played the main role in decomposing organic pollutants. The results of this work would

Enhanced, robust light-driven H<sub>2sub> generation by gallium-doped titania nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Luo, Si [Chemistry Department, Brookhaven National Laboratory; Upton; USA; Department of Chemistry, Stony Brook University, Stony Brook; USA; Nguyen-Phan, Thuy-Duong [Chemistry Department, Brookhaven National Laboratory; Upton; USA; Vovchok, Dimitriy [Chemistry Department, Brookhaven National Laboratory; Upton; USA; Department of Chemistry, Stony Brook University, Stony Brook; USA; Waluyo, Iradwikanari [Photon Sciences Division, National Synchrotron Light Source II, Brookhaven National Laboratory; Upton; USA; Palomino, Robert M. [Chemistry Department, Brookhaven National Laboratory; Upton; USA; Gamalski, Andrew D. [Center for Functional Nanomaterials, Brookhaven National Laboratory; Upton; USA; Barrio, Laura [CSIC – Instituto de Catalisis y Petroleoquimica Cantoblanco; E-28049 Madrid; Spain; Xu, Wenqian [X-ray Science Division, Advanced Photon Source, Argonne National Laboratory; Argonne; USA; Polyansky, Dmitry E. [Chemistry Department, Brookhaven National Laboratory; Upton; USA; Rodriguez, José A. [Chemistry Department, Brookhaven National Laboratory; Upton; USA; Department of Chemistry, Stony Brook University, Stony Brook; USA; Senanayake, Sanjaya D. [Chemistry Department, Brookhaven National Laboratory; Upton; USA

2017-12-14

Successful introduction of gallium ions into TiO<sub>2sub>nanoparticles significantly promotes the H<sub>2sub>evolution activity and stability, increasing the opportunities for designing promising photocatalysts for green fuel production.

Clinical review: optimizing enteral nutrition for critically ill patients - a simple data-driven formula

Science.gov (United States)

2011-01-01

In modern critical care, the paradigm of 'therapeutic nutrition' is replacing traditional 'supportive nutrition'. Standard enteral formulas meet basic macro- and micronutrient needs; therapeutic enteral formulas meet these basic needs and also contain specific pharmaconutrients that may attenuate hyperinflammatory responses, enhance the immune responses to infection, or improve gastrointestinal tolerance. Choosing the right enteral feeding formula may positively affect a patient's outcome; targeted use of therapeutic formulas can reduce the incidence of infectious complications, shorten lengths of stay in the ICU and in the hospital, and lower risk for mortality. In this paper, we review principles of how to feed (enteral, parenteral, or both) and when to feed (early versus delayed start) patients who are critically ill. We discuss what to feed these patients in the context of specific pharmaconutrients in specialized feeding formulations, that is, arginine, glutamine, antioxidants, certain ω-3 and ω-6 fatty acids, hydrolyzed proteins, and medium-chain triglycerides. We summarize current expert guidelines for nutrition in patients with critical illness, and we present specific clinical evidence on the use of enteral formulas supplemented with anti-inflammatory or immune-modulating nutrients, and gastrointestinal tolerance-promoting nutritional formulas. Finally, we introduce an algorithm to help bedside clinicians make data-driven feeding decisions for patients with critical illness. PMID:22136305

Observation of self-organized criticality (SOC) behavior during edge biasing experiment on TEXTOR

Energy Technology Data Exchange (ETDEWEB)

Xu, Y.H.; Jachmich, S.; Weynants, R.R. [Ecole Royale Militaire/Koninklijke Militaire School, Laboratory for Plasma Physics, Euratom-Belgian State Association, Brussels, Belgium, Partner in the Trilateral Euregio Cluster (Belgium)

2004-07-01

The self-organized criticality (SOC) behavior of the edge plasma transport has been investigated using the fluctuation data measured in the plasma edge and the scrape-off layer of TEXTOR tokamak before and during the edge electrode biasing experiments. In the 'non-shear' discharge phase before biasing, both the potential and density fluctuations clearly exhibit some of the characteristics associated with SOC: (1) existence of f{sup -1} power-law dependence in the frequency spectrum, (2) slowly decaying long tails in the autocorrelation function, (3) values of Hurst parameters larger than 0.5 at all the detected radial locations, (4) non-Gaussian probability density function of fluctuations and (5) radial propagation of avalanche-like events in the edge plasma area. During the biasing phase, with the generation of an edge radial electric field E{sub r} and hence a sheared E{sub r} x B flow, the local turbulence is found to be well de-correlated by the E{sub r} x B velocity shear, consistent with theoretical predictions. Nevertheless, it is concomitantly found that the Hurst parameters are substantially enhanced in the negative flow shear region and in the scrape-off layer as well, which is contrary to theoretical expectation. Implication of these observations to our understanding of plasma transport mechanisms is discussed. (authors)

Condensation during gravity driven ECC: Experiments with PACTEL

Energy Technology Data Exchange (ETDEWEB)

Munther, R.; Kalli, H. [Lappeenranta Univ. of Technology (Finland); Kouhia, J. [Technical Research Centre of Finland, Lappeenranta (Finland)

1995-09-01

This paper provides the results of the second series of gravity driven emergency core cooling (ECC) experiments with PACTEL (Parallel Channel Test Loop). The simulated accident was a small break loss-of-coolant accident (SBLOCA) with a break in a cold leg. The ECC flow was provided from a core makeup tank (CMT) located at a higher elevation than the main part of the primary system. The CMT was pressurized with pipings from the pressurizer and a cold leg. The tests indicated that steam condensation in the CMT can prevent ECC and lead to core uncovery.

Curvature-driven instabilities in the Elmo Bumpy Torus (EBT)

International Nuclear Information System (INIS)

Abe, H.; Spong, D.A.; Antonsen, T.M. Jr.; Tsang, K.T.; Nguyen, K.T.

1982-01-01

Curvature-driven instabilities are analyzed for an EBT configuration which consists of plasma interacting with a hot electron ring whose drift frequencies are larger than the growth rates predicted from conventional magnetohydrodynamic (MHD) theory. Stability criteria are obtained for five possible modes: the conventional hot electron interchange, a high-frequency hot electron interchange (at frequencies greater than the ion-cyclotron frequency), a compressional instability, a background plasma interchange, and an interacting pressure-driven interchange. A wide parameter regime for stable operation is found, which, however, severely deteriorates for a band of intermediate mode numbers. Finite Larmor radius effects can eliminate this deterioration; moreover, all short-wavelength curvature-driven modes are stabilized if the hot electron Larmor radius rho/sub h/ satisfies (kappa/sub perpendicular/rho/sub h/) 2 > 2Δ/[Rβ/sub h/(1 + P'/sub parallel//P'/sub perpendicular/)], where kappa/sub perpendicular/ is the transverse wavenumber, Δ is the ring half-width, R is the mid-plane radius of curvature, β/sub h/ is the hot electron beta value, and P' is the pressure gradient. Resonant wave-particle instabilities predicted by a new low frequency variational principle show that a variety of remnant instabilities may still persist

Application of the modified neutron source multiplication method for a measurement of sub-criticality in AGN-201K reactor

International Nuclear Information System (INIS)

Myung-Hyun Kim

2010-01-01

Measurement of sub-criticality is a challenging and required task in nuclear industry both for nuclear criticality safety and physics test in nuclear power plant. A relatively new method named as Modified Neutron Source Multiplication Method (MNSM) was proposed in Japan. This method is an improvement of traditional Neutron Source Multiplication (NSM) Method, in which three correction factors are applied additionally. In this study, MNSM was tested in calculation of rod worth using an educational reactor in Kyung Hee University, AGN-201K. For this study, a revised nuclear data library and a neutron transport code system TRANSX-PARTISN were used for the calculation of correction factors for various control rod positions and source locations. Experiments were designed and performed to enhance errors in NSM from the location effects of source and detectors. MNSM can correct these effects but current results showed not much correction effects. (author)

Dynamic signatures of driven vortex motion.

Energy Technology Data Exchange (ETDEWEB)

Crabtree, G. W.; Kwok, W. K.; Lopez, D.; Olsson, R. J.; Paulius, L. M.; Petrean, A. M.; Safar, H.

1999-09-16

We probe the dynamic nature of driven vortex motion in superconductors with a new type of transport experiment. An inhomogeneous Lorentz driving force is applied to the sample, inducing vortex velocity gradients that distinguish the hydrodynamic motion of the vortex liquid from the elastic and-plastic motion of the vortex solid. We observe elastic depinning of the vortex lattice at the critical current, and shear induced plastic slip of the lattice at high Lorentz force gradients.

Criticality experiments of the years 1981 and 1982

International Nuclear Information System (INIS)

Heinicke, W.; Tischer, A.

1983-01-01

This report presents a collection of published criticality experiments made in 1981 and 1982 and thus continues the collection of experimental data of this type commenced with the GRS report A-644 of November 1981, which covers criticality experiments of the years 1975 to 1980. The report gives the main data of about 30 publications which, just a those cited in the GRS report, can be retrieved from the improved KRITEXP data base using 14 index terms, and printed out at random sequence. The collection of experimental data is of particular value with regard to the licensing of all installations forming part of the nuclear fuel cycle, which is subject to the atomic energy law and requires the verification of computed criticality analyses by experimental data. (orig.) [de

Electron cyclotron current drive experiments on DIII-D

Energy Technology Data Exchange (ETDEWEB)

James, R.A. (Lawrence Livermore National Lab., CA (USA)); Giruzzi, G.; Gentile, B. de; Rodriguez, L. (Association Euratom-CEA, Centre d' Etudes Nucleaires de Cadarache, 13 - Saint-Paul-les-Durance (France)); Fyaretdinov, A.; Gorelov, Yu.; Trukhin, V. (Kurchatov Inst. of Atomic Energy, Moscow (USSR)); Harvey, R.; Lohr, J.; Luce, T.C.; Matsuda, K.; Politzer, P.; Prater, R.; Snider, R. (General Atomics, San Di

1990-05-01

Electron Cyclotron Current Drive (ECCD) experiments on the DIII-D tokamak have been performed using 60 GHz waves launched from the high field side of the torus. Preliminary analysis indicates rf driven currents between 50 and 100 kA in discharges with total plasma currents between 200 and 500 kA. These are the first ECCD experiments with strong first pass absorption, localized deposition of the rf power, and {tau}{sub E} much longer than the slowing-down time of the rf generated current carriers. The experimentally measured profiles for T{sub e}, {eta}{sub e} and Z{sub eff} are used as input for a 1D transport code and a multiply-ray, 3D ray tracing code. Comparisons with theory and assessment of the influence of the residual electric field, using a Fokker-Planck code, are in progress. The ECH power levels were between 1 and 1.5 MW with pulse lengths of about 500 msec. ECCD experiments worldwide are motivated by issues relating to the physics and technical advantages of the use of high frequency rf waves to drive localized currents. ECCD is accomplished by preferentially heating electrons moving in one toroidal direction, reducing their collisionality and thereby producing a non-inductively driven toroidal current. 6 refs., 4 figs.

Synthesis, optical properties and photodegradation for methylene blue of Ni-vanadate K{sub 2}Ni(VO{sub 3}){sub 4} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Lu, Yuting; Pu, Yinfu; Huang, Yanlin, E-mail: huang@suda.edu.cn; Wang, Jing; Lu, Juan, E-mail: lujuan@suda.edu.cn, E-mail: juanlu@suda.edu.cn [Soochow University, College of Chemistry, Chemical Engineering and Materials Science (China)

2015-11-15

A Ni{sup 2+}-containing vanadate, K{sub 2}Ni(VO{sub 3}){sub 4} was developed as a new visible-light-driven photocatalyst. The nanoparticles were prepared by the modified Pechini method. The sample was characterized by the measurements such as X-ray powder diffraction, scanning electron microscope, and UV–Vis absorption spectrum. The photocatalytic activity of K{sub 2}Ni(VO{sub 3}){sub 4} nanoparticles was evaluated by the photodegradation of methylene blue under visible-light irradiation in air. K{sub 2}Ni(VO{sub 3}){sub 4} shows a photocatalytic activity due to the efficient absorption in the UV–Visible-light wavelength region with a narrowed band-gap energy of 2.08 eV and an indirectly allowed electronic transition. These results indicate that this vanadate garnet could be a potential photocatalyst driven by visible light. The effective photocatalytic activity was discussed on the basis of the special structural characteristic such as heavily distorted NiO{sub 6}, rich, activated optical centers with tunnel structure for high photocatalytic capacity, and discussed on the basis of the photoluminescence and the decay lifetime.

Critical thickness for strain relaxation of Ge{sub 1−x}Sn{sub x} (x ≤ 0.17) grown by molecular beam epitaxy on Ge(001)

Energy Technology Data Exchange (ETDEWEB)

Wang, Wei; Zhou, Qian; Dong, Yuan; Yeo, Yee-Chia, E-mail: yeo@ieee.org [Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117576 (Singapore); Tok, Eng Soon [Department of Physics, National University of Singapore, Singapore 117551 (Singapore)

2015-06-08

We investigated the critical thickness (h{sub c}) for plastic relaxation of Ge{sub 1−x}Sn{sub x} grown by molecular beam epitaxy. Ge{sub 1−x}Sn{sub x} films with various Sn mole fraction x (x ≤ 0.17) and different thicknesses were grown on Ge(001). The strain relaxation of Ge{sub 1−x}Sn{sub x} films and the h{sub c} were investigated by high-resolution x-ray diffraction and reciprocal space mapping. It demonstrates that the measured h{sub c} values of Ge{sub 1−x}Sn{sub x} layers are as much as an order of magnitude larger than that predicted by the Matthews and Blakeslee (M-B) model. The People and Bean (P-B) model was also used to predict the h{sub c} values in Ge{sub 1−x}Sn{sub x}/Ge system. The measured h{sub c} values for various Sn content follow the trend, but slightly larger than that predicted by the P-B model.

Properties of the (Sm sub 0 sub . sub 3 sub 3 Eu sub 0 sub . sub 3 sub 3 Gd sub 0 sub . sub 3 sub 3)Ba sub 2 Cu sub 3 O sub y superconductor prepared by different processes in air

CERN Document Server

Giovannelli, F; Monot-Laffez, I

2003-01-01

Bars and pellets of the (Sm sub 0 sub . sub 3 sub 3 Eu sub 0 sub . sub 3 sub 3 Gd sub 0 sub . sub 3 sub 3)Ba sub 2 Cu sub 3 O sub x superconductor were processed in air, using the floating zone method and the top-seeded melt-textured growth method, respectively. The samples were prepared using different experimental conditions, i.e. maximal processing temperature, translation rate or cooling rate. Their physical properties and their microstructure were studied. All the samples exhibit a satisfying superconducting transition whereas the critical current density greatly depends on the processing parameters. The sample prepared by the floating zone method at 1070 deg C with a translation rate of 2 mm h sup - sup 1 exhibits a very high J sub c value of 70000 A cm sup - sup 2 in the self-field and more than 30000 A cm sup - sup 2 at 1.7 T. The pellet processed at 1080 deg C with a cooling rate of 2 deg C h sup - sup 1 has a high J sub c reaching about 56000 A cm sup - sup 2 in the self-field and more than 32000 A ...

Search for {nu}{sub {mu}}{yields}{nu}{sub {tau}} neutrino oscillations in the {tau}{sup -}{yields}e{sup -}{nu}-bar{sub e}{nu}{sub {tau}} decay channel in the Nomad experiment at CERN

Energy Technology Data Exchange (ETDEWEB)

Popov, B.A

1998-05-01

This work has been done in the framework of the NOMAD experiment at CERN. It is devoted to the {nu}{sub {mu}} {yields} {nu}{sub {tau}} oscillation search in the {tau}{sup -} {yields} e{sup -}{nu}-bar{sub e}{nu}{sub {tau}} decay channel. After a brief reminder on the neutrino properties and a short review of the experimental searches for neutrino oscillations, the description of the NOMAD experiment is given. The event reconstruction in the NOMAD experiment is presented with a special emphasis put on the electron identification and reconstruction. The track model used for the charged track reconstruction is described in details. The algorithm developed to treat electron trajectories in the NOMAD setup based on the sub-detector matching technique and the breakpoint search algorithm is presented. The quality of the reconstruction of the kinematics of neutrino interactions is illustrated. It is shown that the currently used detector simulation program cannot reproduce precisely the behaviour of the hadronic jet observed in the NOMAD real data especially in the plane perpendicular to the incoming neutrino direction. To overcome this problem simulations based on the real data are used whenever possible. The method based on the likelihood ratio is developed to discriminate a signal from a background. A selection of {nu}{sub e} CC candidates from the NOMAD '96 data set is performed using this technique. 1842 events are extracted with a selection efficiency of (38.5 {+-} 0.5%) while the background contamination is estimated to be less than 0.5%. This number of events is compatible with our expectations: 1891 {+-} 25(stat){+-} 95(syst). No sign of possible {nu}{sub {mu}} {yields} {nu}{sub e} oscillation signal corresponding to the LSND solution in the large {delta}m{sup 2} region is observed in the NOMAD data. Finally, the preliminary analysis of the {nu}{sub {mu}} {yields} {nu}{sub {tau}} oscillation search in the {tau}{sup -} {yields} e{sup -}{nu}-bar{sub e}{nu}{sub

Criticality Experiments Performed in Saclay and Valduc Centers, France (1958-2002)

International Nuclear Information System (INIS)

Barbry, F.; Grivot, P.; Girault, E.; Fouillaud, P.; Cousinou, P.; Poullot, G.; Anno, J.; Bordy, J.M.; Doutriaux, D.

2003-01-01

Since 1958, the Commissariat a l'Energie Atomique and then the Institut de Radioprotection et de Surete Nucleaire (previously the Institut de Protection et de Surete Nucleaire) have carried out criticality experiments first in Saclay and then in the Valduc criticality laboratory. This paper is a survey of the programs conducted during the last 45 yr with the different apparatuses. This paper also gives information about plans for the future. Programs are presented following the chronology and the International Criticality Safety Benchmark Evaluation Project classification. Among the numerous series of experiments, now 22 series (corresponding to 407 configurations) have been included in the 'International Handbook of Evaluated Criticality Safety Benchmark Experiments'

Bibliography for nuclear criticality accident experience, alarm systems, and emergency management

International Nuclear Information System (INIS)

Putman, V.L.

1995-09-01

The characteristics, detection, and emergency management of nuclear criticality accidents outside reactors has been an important component of criticality safety for as long as the need for this specialized safety discipline has been recognized. The general interest and importance of such topics receives special emphasis because of the potentially lethal, albeit highly localized, effects of criticality accidents and because of heightened public and regulatory concerns for any undesirable event in nuclear and radiological fields. This bibliography lists references which are potentially applicable to or interesting for criticality alarm, detection, and warning systems; criticality accident emergency management; and their associated programs. The lists are annotated to assist bibliography users in identifying applicable: industry and regulatory guidance and requirements, with historical development information and comments; criticality accident characteristics, consequences, experiences, and responses; hazard-, risk-, or safety-analysis criteria; CAS design and qualification criteria; CAS calibration, maintenance, repair, and testing criteria; experiences of CAS designers and maintainers; criticality accident emergency management (planning, preparedness, response, and recovery) requirements and guidance; criticality accident emergency management experience, plans, and techniques; methods and tools for analysis; and additional bibliographies

Study of the magnetic properties of CeCu{sub 2}(Si{sub 1-x}Ge{sub x}){sub 2} by means of neutron scattering; Untersuchung der magnetischen Eigenschaften von CeCu{sub 2}(Si{sub 1-x}Ge{sub x}){sub 2} mittels Neutronenstreuung

Energy Technology Data Exchange (ETDEWEB)

Faulhaber, Enrico

2008-07-01

In 1979 the first heavy-fermion superconductor CeCu{sub 2}Si{sub 2} was discovered by Steglich et al. The system is near a quantum critical point (QCP), where the magnetic order is just suppressed. The distance to the QCP can be varied with hydrostatic pressure as well as by germanium substitution on the silicon site. Next to the superconductivity in CeCu{sub 2}Si{sub 2} one finds distinct magnetic phases while increasing the germanium content. CeCu{sub 2}Si{sub 2} shows a magnetic order of a spin-density-type below T{sub N}-0.8 K, whereas the heavy fermion system CeCu{sub 2}Ge{sub 2} orders below T{sub N}=4.1 K as an antiferromagnet. The focus of this thesis is on neutron-diffraction in the system CeCu{sub 2}(Si{sub 1-x}Ge{sub x}){sub 2}. Starting with a sample with a high germanium content of x=0.45, the magnetic structures are investigated in detail. Following a step-by-step approach, samples with reduced x are investigated subsequently to figure out the properties of pure CeCu{sub 2}Si{sub 2}, which were not accessible before. Furthermore, the complex interaction between magnetism and superconductivity is investigated in detail. Using a specially designed setup, the ac-susceptibility could be recorded simultaneously during the neutron diffraction experiments. Due to the direct correlation between antiferromagnetic signals and diamagnetic features, the microscopic coexistence of superconductivity and magnetic order can be ruled out. Instead, a phase separation on the microscopic scale is found. (orig.)

Optimization of current waveform tailoring for magnetically driven isentropic compression experiments

Energy Technology Data Exchange (ETDEWEB)

Waisman, E. M.; Reisman, D. B.; Stoltzfus, B. S.; Stygar, W. A.; Cuneo, M. E.; Haill, T. A.; Davis, J.-P.; Brown, J. L.; Seagle, C. T. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Spielman, R. B. [Idaho State University, Pocatello, Idaho 83201 (United States)

2016-06-15

The Thor pulsed power generator is being developed at Sandia National Laboratories. The design consists of up to 288 decoupled and transit time isolated capacitor-switch units, called “bricks,” that can be individually triggered to achieve a high degree of pulse tailoring for magnetically driven isentropic compression experiments (ICE) [D. B. Reisman et al., Phys. Rev. Spec. Top.–Accel. Beams 18, 090401 (2015)]. The connecting transmission lines are impedance matched to the bricks, allowing the capacitor energy to be efficiently delivered to an ICE strip-line load with peak pressures of over 100 GPa. Thor will drive experiments to explore equation of state, material strength, and phase transition properties of a wide variety of materials. We present an optimization process for producing tailored current pulses, a requirement for many material studies, on the Thor generator. This technique, which is unique to the novel “current-adder” architecture used by Thor, entirely avoids the iterative use of complex circuit models to converge to the desired electrical pulse. We begin with magnetohydrodynamic simulations for a given material to determine its time dependent pressure and thus the desired strip-line load current and voltage. Because the bricks are connected to a central power flow section through transit-time isolated coaxial cables of constant impedance, the brick forward-going pulses are independent of each other. We observe that the desired equivalent forward-going current driving the pulse must be equal to the sum of the individual brick forward-going currents. We find a set of optimal brick delay times by requiring that the L{sub 2} norm of the difference between the brick-sum current and the desired forward-going current be a minimum. We describe the optimization procedure for the Thor design and show results for various materials of interest.

Experiment to investigate anti ν/sub μ/ → anti ν/sub e/ oscillations at Los Alamos Meson Physics Facility

International Nuclear Information System (INIS)

Kruse, H.W.; Toevs, J.W.

1981-01-01

An experiment, being planned at LAMPF, aims to investigate a possible neutrino oscillation channel, anti ν/sub μ/ → anti ν/sub e/. If anti ν/sub μ/, produced in the LAMPF beam stop, oscillate to anti ν/sub e/, then interactions anti ν/sub e/ + p → e + + n, may be detected. A large volume liquid scintillator (4470 liter) emplaced at 33 m from the beam stop, detects e + and n, after moderation in the hydrogenous liquid and capture in Gd, loaded into the scintillator. Our anticipated signal rate is currently estimated at 1.67 (sigma m 2 ) 2 /day assuming full amplitude oscillation. The corresponding counting rate, assuming all anti ν/sub μ/ have oscillated to anti ν/sub e/ at the detector is 1.5/day. Cosmic rates are estimated at 0.033/day. Correlated backgrounds from the beam stop are calculated to be small in comparison to cosmic events, except for reactions of ν/sub e/ in Pb. These reactions may be reduced with an Fe shield within the detector. With the above rate, a limit on the sensitivity of our experiment for the value of sigma m 2 is estimated at 0.12 eV 2 with 70 days of counting. Detector features, estimated background rates, and sensitivity values are discussed

The magnetic properties of oxide spinel Li{sub 0.5}Fe{sub 2.5-2x}Al{sub x}Cr{sub x}O{sub 4} solid solutions

Energy Technology Data Exchange (ETDEWEB)

Masrour, R., E-mail: rachidmasrour@hotmail.com [Laboratory of Materials, Processes, Environment and Quality, Cady Ayyed University, National School of Applied Sciences, Sidi bouzid, Safi (Morocco); LMPHE, Faculte des Sciences, Universite Mohamed V, Rabat (Morocco); Hamedoun, M. [Institute for Nanomaterials and Nanotechnologies, MaScIR, Rabat (Morocco); Academie Hassan II des Sciences et Techniques, Rabat (Morocco); Benyoussef, A. [LMPHE, Faculte des Sciences, Universite Mohamed V, Rabat (Morocco); Institute for Nanomaterials and Nanotechnologies, MaScIR, Rabat (Morocco); Academie Hassan II des Sciences et Techniques, Rabat (Morocco)

2012-04-01

The exchange interactions (J{sub BB} and J{sub AB} are the intra and the inter-sublattice exchange interactions between neighbouring spins, respectively) are obtained by using the general expressions of canting angle and critical temperature obtained by mean field theory of Li{sub 0.5}Fe{sub 2.5-2x}Al{sub x}Cr{sub x}O{sub 4}. The expression of magnetic energy of Li{sub 0.5}Fe{sub 2.5-2x}Al{sub x}Cr{sub x}O{sub 4} is obtained for different spin configurations and dilution x. The saturation magnetisation of Li{sub 0.5}Fe{sub 2.5-2x}Al{sub x}Cr{sub x}O{sub 4} is obtained with different values of dilution x. The magnetic phase diagram of Li{sub 0.5}Fe{sub 2.5-2x}Al{sub x}Cr{sub x}O{sub 4} materials is obtained by high temperature series expansions (HTSEs). The critical exponent associated with the magnetic susceptibility of Li{sub 0.5}Fe{sub 2.5-2x}Al{sub x}Cr{sub x}O{sub 4} is deduced.